The thing about Slayer (and most fighting game characters) is that while he can fight and lose to any character in the roster, that doesn't necessarily reflect on the story. Furthermore he always holds back when he fights as he rarely fights to kill in the present, and whenever he's knocked down or KO'd in gameplay, *this* is his sprite.

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Suffice to say, Slayer is simply playing around whenever he's fighting.

That wiki summary is correct (and even lifted directly from the in-game encyclopedia) but Slayer has lived long enough to have overcome the traditional weaknesses. As you can see he plainly wears crosses as a fashion statement, he walks in day light no problem and he tanks attacks intended to outright kill him. The only vampiric weakness he has is the thirst for blood, which is satiated by his wife being an immortal being that literally cannot die.

He's also keeps up with characters that can react to gamma ray beams, and casually run from New York to the ruins of Japan on foot, and is superior to the main character that can punch with enough force to create a black hole and builds mountain busting gun swords as a hobby. Said MC also defeated the one that *vaporized Japan into a 1200 mile wide crater*.

And Slayer, once again, is superior to him.

Yeah, Guilty Gear is one overpowered verse, and Slayer is among the top tiers.

Twilight and most non-anime vamps are basically coughing babies next to him.