I consider finishing a game as completing it in the highest level of difficulty. Comes to mind:
- Dragon Age Inquisition (finished on Nightmare, but with no FF as it is so annoying to do with KB&M)
- Far Cry (came close in normal difficulty, didn't have the patience)
- C&C 3 (multiplayer balance patches screwed up the campaign)
- Crysis (finished on normal, no intention to play a second time)
- Unreal Tournament (I was at the time one of the best Flak Cannon users in Israel, but didn't have the ability nor the patience to finish the single player on Godlike)
- Starcraft 2 Wings of Liberty (finished on Normal the campaign, didn't on Brutal, but did reach Masters so I guess I did finish a half of it)
- Diablo 2 LoD (Criterion: finishing Hell on Hardcore. I'm too bad at Hardcore... maximum I've reached is act 3 Nightmare)