Well, Alice is a weapon. She's bound to be at least as strong as Wesker is, seeing if it's RE5 related power. They'd at least be on same level. Nemesis is a completely different level of power, seeing as he was meant to be created for near invincibility. And about the clones, you can't say yet whether or not that they'd be at Alice's level of strength, seeing as she is the original product of the Alice project. I mean, she got impaled at the end of the second movie, she is definitely powerful. Not to mention in the third film, she has telekinesis. So there is definitely a way Alice can beat Wesker.