What are some Bad plot twist that annoy you?

[Riachu]

Kantor said:

I hate it when somebody is your ally for half the game, and then it turns out that they're EVIL just as you're starting to like them.

Examples:

Harry Flynn

Alister Azimuth (kind of)

The latter was not evil.  His motives just got the best of him and was already too late when he realized it.