the hardest game I've played is the original Mario!
ready...
set?...
GOOOO!
Edit 1: Thanks for all the replies guys! 300+ and counting I love it!
Edit 2: 500+ hole cow thanks guys! keep posting!
Edit 3: .........1000+........COMMENTS
WHOOHOO!!!
Edit 4 I hear 2000 calling my name!
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OG Metroid. Kraid alone is a ridiculously hard boss unless you have all full energy tanks. For individual levels, Gravemind LASO is apparently next to impossible, and actually is impossible solo.