The time lords could just throw the Doctor at team 2 and he'd somehow kill them all off after running a lot and spouting some vague technobabble, like he always does.

Time Lords all the way

Since I see there is not that much activity here, I'll list the biggest things each verse has and how would they factor: Mass Effect: I don't think the Alliance or the Council species can do much against the Time Lords. Mass Accelerators cannot harm any weapon the Time Lords pull out, such weapons are considered to be... like the clubs of caveman, considering that they consider a control panel for every star in the universe a rudimentary weapon not worth of mass producing. I don't think others like the Protheans or the Rachni are of much use. The Reapers are some of the greater threats in Mass Effect, but I don't see them even taking out a single War TARDIS without much effort. Indoctrination, however, if used correctly, could manage to turn renegade Time Lords againts their species, which would be an adventage if they manage to keep them on a mentally healthy state such as those of Saren and the Illusive Man, instead of fanatics. And that takes me to the Leviathans, as if their enthralling artifacts are powerful enough, they could obtain something powerful from the Time Lords, and I'm not talking a single individual, but a TARDIS. If they can enthrall a TARDIS' intelligence (which I doubt, but I'm not completely sure of the mental faculties of one) then It would be useful. A War TARDIS, even better. However, enthralling a Capital Ship Reaper I think is orders of magnitude below of enthralling ANY TARDIS, even an outdated one like the Doctor's. But you say, as a CS Reaper contains the consciousness of millions, even billions, of people. Starcraft: The Terrans are at least planet busters in this universe. But they don't have access to many things above Apocalypse class nukes (those planet busting nukes), even when the marines have hax armor. The Zerg are another story, as there are billions of them, are advanced enough to warp planets through wormholes, and can assimilate species to boost themselves (hell, the Zerg supervirus turned A -blam!-ING WORM into an Hydralisk). The Zerg Overmind is a massively powerful pyschic eldritch abomination on par or below with a Gravemind, as it is able to mind -blam!- anyone within its range and control every Zerg. Then we got Queen of Blades Kerrigan, who was a massively powerful infested Terran pyschic that took control of the whole Zerg Swarm, was one or two orders of magnitude above the Terran pyschic scale and she was at the top when she was human, could create storms of pyschic energy like the Protoss and could mind -blam!- a Protoss Matriarch (Dark Templar I think) while being on A DIFFERENT PLANET. Primal Zerg Kerrigan is above even the Queen of Blades, seeing as she has now Primal Zerg DNA, pure Zerg DNA instead of the tainted one the Swarm possesses. In this state she is the most powerful psychic in Starcraft Universe, above any Protoss, and her power couldn't be measured by the Terran scale (her Queen of Blades form's power could still be calculated by the scale even if she wasn't classified). The Protoss are beings of energy with incredible psychic control who can fuse between each other to become Archons, beings of pure psychic energy. The Dark Templar faction of the Protoss control the power of the Void (if someone is more knowledgeable than me on this subject please add). The Protoss are dangerous in here because they have the tech to glass and bust planets (they should be orders of magnitude above the Terrans at doing this) and their Motherships have black hole generators. Yes, freaking black holes, much better than supernovae (Even when a supernova would destroy the star system, a black hole would shallow it with a force so great that the atomic structures of every thing would have been torn apart, not even light escapes, and the system is completely crushed). The Xel'naga are nearly an unknown but they are the creators of the Protoss and the Zerg (in fact, these two species combined would create another itineration of Xel'naga). Their structures and artifacts are powerful enough to create energy beings which have shown disintegration powers. They've got worldships, and they seem to be incredibly powerful psychics. Amon is believed to pack the power of Kerrigan's Queen of Blades form plus more, and a Hybrid (perverted versions of the Xel'naga created by the combination of Protoss and Zerg) could mind -blam!- an entire planet. The Halo Universe is the most dangerous of the bunch due to the Forerunners and the Precursors. The UNSC and the Covenant are fodder. While the UNSC are incredibly above the Mass Effect Alliance, they are below Starcraft's Terrans (regular marines can brawl with an Spartan). The maximum showing of the UNSC is planet busting via NOVA Bomb. The Covenant would be above even the Reapers, but they are below the Protoss (their maximum showing is planet glassing. That has nothing on creating black holes, which shallow star systems, besides the fact that the Protoss can glass planets with ease and a single Protoss is above an Elite by the sheer virtue of raw psychic power and broken psychic storms). The Forerunners are more powerful than any civilization previously mentioned, they were able to shift the axis of galaxies, devolve species as powerful as they were, and use Keyships to make suns go supernova and thus wipe out star systems with ease (one Keyship soloed an Elite fleet, even when the Prophets didn't know how to operate it). They had access to the Domain, a metaphysical database of the Precursors (which was, in fact, a Precursor in itself). They could use light to build structures, including ships. Their ships were hundreds of kilometers long, and their combat skins were orders of magnitude above MJOLNIR Armor, causing visible damage to a planet from orbit. Their War Sphinxes were even more impressive, can get into space and can bust cities. They are used in continental scale bombardements and are only considered "midsized battle suits". They used light and antimatter in their hand weaponry. Their AI were advanced enough to control entire fleets and be tactical geniuses. They were able to create Dyson Spheres as habitable planets and place them in another dimension, Slipspace, which they were complete masters of. They even travelled to other dimensions. They had limited time tech, such as timelocks which could age anything to the point of death in seconds. Their maximum showing is the Halo Array, which wiped a whole galaxy of all of its life and was able to destroy the nearly indestructible Neural Physic constructs of the Precursors. Now the Precursors. They are complete beasts. A transsentient species which was able to travel through galaxies and supossedly predates the universe, and are infinitely more advanced than the Forerunners. They created every form of life in the galaxy, including the Forerunners and Mankind. The Precursors created constructs out of Neural Physics, or in other words, thought. The structures were indestructible to anything but the Halo Array. The Precursors could change their forms and exist as whatever they wanted, be them corporeal beings, incorporeal beings... Their last form, which they are using for vengueance purposes, is The Flood. As the Flood, the Precursors can infect anything with enough biomass, including machinery, and the collective Precursor intelligence is represented by the Graveminds, which control everyone, have the aggregate of the minds of the infected and can corrupt any Forerunner AI, and pretty much mind -blam!- anyone near them. The Gravemind (or Precursor) intelligence is a metaphysical entity that won't dissapear as long as a single Flood spore remains, even if the physical body of the Gravemind is killed. The Flood has numerous forms that are very powerful troops. When a Gravemind absorbs an entire planet's biomass, it evolves into its final stage, a Key Mind. In this state, the full Precursor intelligence is revealed which lends it more intelligence than even the most advanced Forerunner AI and the ability to control Precursor technology. Here it comes, Star Roads, roads made of Neural Physics which connect star systems and are indestructible. With the Key Mind in control of them, they can be used to destroy anything from planets to star systems, and to make Forerunner tech and Slipspace travel useless (and remember, the Forerunners were masters of Slipspace). At the stage in which the Key Mind appears, its corruption of AI begins to spread from one to another. The mere presence of Flood at this stage warps the space-time continuum. The Key Mind can even project images of the infected to use as psychological weapons. The power of the Precursor to select forms is so high that the Domain, the metaphysical database of Precursor knowledge the Forerunners used, was a Precursor in its selected form. Now, for the Time Lords. I expect that everyone knows that the Time Lords are one of the top dog races in Doctor Who. Well, their names say everything about them. They are the [i]Lords of Time[/i]. A single Time Lord isn't much of a threat, it is still superhuman due to exposition to the Time Vortex. Most Time Lords have demonstrated psychic power, The Doctor and the Master have mind controlled people, erased their memories and read their minds on multiple ocassions. One individual Time Lord, Salyavin, could control the minds of every individual in the universe. The physical faculties of a Time Lord are beyond those of humans as well, but not by much. Technology, oh GOD, now shit gets real. Their tech granted the Time Lords mastery over time. Their ships, called TARDIS, were massively FTL ships which could travel through time and space. They could travel between galaxies and to every place in the Universe nearly instantaneously, and they could travel to any point in time, past and future. They could manipulate and change events on a whim, making the Universe their domain.

Who or what is Omega?

The Hanar race alone could wipe everyone out, mass effect obviously.

Um. You have trillions of Zerg,Flood and Forerunners to deal with. If the precursors are allowed then i see no reason for the Xel'naga not to be, we know just as little of them.