From strongest to weakest. I did not bother factoring in the AVP Predators but most would fall just above 2 (If taken at pure face value) or (If considering the neutered depictions of their Prey.) 1.
6: Feral (Takes tons of damage from being stabbed repeatedly with various weaponry types, stabbed through the chest with his own spear, getting shot in the back of the head and continuing on the hunt regardless, losing a mandible and an arm and not stopping until eventually brained with a large spear, greater height and mass than the average Predator, most impressive feat of strength on-screen with the bear fight.)
5: Upgrade (Takes a ludicrous amount of damage, height and mass give him the ability to perform greater feats of strength than other Predators.)
4: City Hunter/Berserker Predator (Both take shrapnel and several blows to the chest and torso and walk away from it, but are undone by being brutalised with their own weaponry funnily enough both losing their left arm just like Feral.)
3: Fugitive (Survives a great deal of punishment, shows several exceptional feats of strength, and even on death's door survives although briefly until decapitated.)
2: Jungle Hunter/Classic Predator (Easily has one of the best of the best of the world's elite warriors by the throat literally, obviously skilled, but not that durable if incredibly strong by Predator standards.)
1: Tracker/Falconer (Both show not all that much to differentiate them from the strength of a particularly fit human being only one instance each, lifting a full grown man with a single hand for one and tossing one with the other, both perish to wounds that would kill a human being and show no instances of any exceptional durability beyond that.)
For clarity, when using slash here, I am giving a slight edge to the first name featured by the number.