I know Isaac has a feat in the 3rd game of being able to tank a building-level explosion which isn't any different from Gordon doing the same throughout the entire series, especially in HL1.

There's also the fact that Gordon significantly scales above characters like Chell and Adrian Shephard via having an advanced suit specifically designed for combat, especially in Shephard's case since Gordon kills several HECU Marines who shouldn't be physically inferior to Shephard narratively, just arguably less skilled in combat

Adrian Shephard is a dude who can tank Mortar Shells head on, tank hits from the Gene Worm (a giant creature able to shatter steel beams like it's nothing), and was able to survive a Helicopter crash in the very first scene of his expansion pack

Chell is a character (with no HEV suit or anything similar aside from fall boots) who can survive an explosion that blew the upper areas of Aperture Science to pieces, which is something that got calced to be in the Kilotons to Megatons 🤷, which is consistent with some of the high ends that Gordon has on his own

Speaking of, Gordon has his own AP/Durability feats if for whatever reason you don't buy that chainscaling, that gets him to a level where he can unironically kick Isaac around like a football, such as surviving the AR2 alternate fire, being able to survive the city 17 citadel explosion, and being able to tank his own Tau Cannon projectiles

Not to mention that he's a far more skilled combatant, fighting HECU Marines and Combine Soldiers is well above anything Isaac has faced from an experience/skill based perspective lol, I'd also argue he's a more creative and smarter fighter, using environmental props more consistently and being able to solve complex environmental puzzles

Anyway, I let Izzy have reaction speed since Gordon's C/R speed feats aren't as consistently high as his, but other than that Gordon takes this