I'd say he's stronger than Tifa for a couple reasons:

-he lifted the entire Davey Crockett rifle and warhead easily with one hand. Recoilless rifles of that size in real life are about 300-400 pounds IIRC.

He also punched through armor thick enough that it wasn't even scratched by RPG-7 rounds.

Did I mention he also keeps rifle rounds on his knuckles? He uses them in conjunction with his punches so that when he hits you, he makes the round explode...it's a punch + a bullet right to the face.

Anyone else remember when Volgin groped EVA'S breasts while simultaneously electrocuting her? Awesome.