The only reason it's always singled out as the most "op" weapon is because it's the easiest gun to tell you got killed by. The last word and red death are just as common but don't get nearly as much hate. I'm sure if they turned your screen green they would. Just my 2 cents.
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The truth is thorn is a crutch weapon. It doesn't take much skill to use to get a kill. Just shoot and pray then run away. With the others you actually have to legit kill someone.