can it 1v5

Depends how fed.

No, but depends.

full build for vayne and 4 items on each with annies passive ready for stun

Well that's only over 5 seconds of lockdown so no. No ADC can survive being locked down for that long, doesn't matter how fed as they will have used their gold to build damage, not enough tank items to survive being locked down for essentially forever.

No. Too much reliable cc.

How fed?

And define 1v5, what some people consider to be 1v5 is actually just 1 vs 5 people playing badly 1 at a time

No. Annie stun + Sona stun is too much for Vayne. She can QSS one of them, but not both.

Not possible, volibears in there. Enough said

Unless they play it super bad and go in 1 by 1, Vayne's not gonna do it. 1v5ing in general against a coordinated team is like impossible, u gotta be insanely fed, and if you're insanely fed... well it means they're not coordinated.