1) Internet Forums: "Original poster". The creator of the post to which the comment refers.
2) Gaming (both videogaming and tabletop RPG): "Over powered". A character, weapon, ability so strong that the game lacks challenge and becomes mundane.
1) Post: "Hitler was okay, I guess."
Commenter 1: "OMG! That's so offensive!"
Commenter 2: "Stop being butthurt. OP is probably just a troll."
2) Me: "Ugh, this dungeon is so easy! Our team just wiped out that owl-bear with three sneak attacks."
Friend: "Well, it's either because two of us are rouges or because the GM made us OP by having us challenge the harder dungeon first."