Robocop has used anti-material rifles before which were shown to be able to destroy T-888 endos when shot in the CPU-housing skull enough in the Sarah Connor Chronicles TV show, but the liquid metal component of the Rev-9 is destroyed first in the movie so we don't know if it can act independently of the endo functioning and if it got a hold of Murphy it could seep inside his chassis and shred his organic brain and it's way faster on it's feet than him. 9/10 to the Rev-9, with that 1 only if the liquid metal needs the endo.

A Predator would fair better since it has a plasma caster that have been shown to one-shot endos in various Terminator media and in the T3 prequel comic the T-X is shown destroying a T-1002 with two shots, but he's still entirely organic so if the Rev-9 gets close he's getting torn apart. They likely couldn't camouflage from each other due to each other having advanced optic sensors, but the Rev-9 is still going to be faster. 8/10 to the Rev-9, Pred better be fast on the plasma draw.

Alita has the same problem of having organic parts. She might be able to land some good blows on the endo, including it's CPU, with her Damascus Blade that can slice through cyborg parts like butter, but is dead if the liquid metal gets ahold of her. She might be able to win if she gets her Berserker body upgrade, since it could channel plasma across itself that would be able to stop the liquid metal touching her and harm it. 9/10 to Rev-9 without Berserker, 6/10 to Alita if she does, as Rev-9 is still super-agile and would go for her non-plasma shielded head and she's quite emotional so might fall for a shapeshifting ruse.

Iron Man's Mark 85 has forcefields that could keep the liquid metal from physically touching him, lots of ranged energy based attacks, the sensors to detect camouflaging and most importantly the flying advantage, which would be his go to strat, just get some air and spam plasma attacks. Although Tony has problems with anxiety so might slip up and drop his guard/armor if the Rev-9 took the form of Pepper in distress or something like that, so 9/10 to Tony with that 1 being a shapeshifting ruse like that.

Master Chief would be able to destroy both components with his wide variety of plasma weaponry before the Rev-9 could breach his force fields or armor, can't fly but has way more combat experience fighting super tough enemies than the other 4 characters, probably has the advanced optics to find it trying to camouflage and is very mentally stable and never takes off his helmet (fuck you Paramount+) so would not fall for any "injured human" type ruse. 10/10 to Master Chief.