Birkin wasn't much of an antagonist before his mutation, but yeah his first form, where he shadows his human appearance but has the arms and talons and all.

They were the dynamic duo for sure, I loved them in RE0, and I wish we could have seen more of them...
I have a top 5 thing I usually do:
1. Wesker
2. William
3. Spencer
4 & 5. Alternate among the these three, Chris, Jill & Claire.
What is your top 5?