Resident Evil 6 is arguably the worst game in the series, with its total focus on action over suspense. But another frustrating aspect of the game was its repetition.
Nowhere is this more evident than in the appearances of Derek Simmons -- who is not only quite a bland villain, but one you get tired of seeing. Because you're forced to face him 6 times...with a frustrating and difficult final battle at the end.
I can see where Capcom was trying to go with these encounters, as it seemed like they were trying to recreate the Nemesis scenes from Resident 3. But instead it had the complete opposite effect, with this character more than outstaying his welcome. Not too long into the game, his appearances became more eye-rolling than nerve-shattering.