Really difficult to say. Lobo's power is 100% physical, but oh boy, there's a lot of it. Plus he has the ability to regenerate himself from a single drop of his blood... or become an army of himself. Plus he is a murderous brute, but he can be clever if he needs to be... he created the plague that exterminated all life on his homeworld himself, after all.
...Did we cover Doomsday yet?
Doomsday... the supreme survival machine. Created hundreds of thousands of years ago on the then-savage world of Krypton to be the ultimate life form by simply placing a child in the incredibly hostile environment, retrieving the remains, cloning it, and repeating it thousands of times, a being emerged that could adapt to anything. If killed, it regenerates - but altered, so it cannot be defeated the same way twice.
Killing him at all is hard enough, though; when he first appeared on Earth, he was as strong as Superman and the two fought each other to death after he had torn through the Justice League. He obviously kept returning, each time more powerful than the last. Sometimes, his evolution makes him stronger in one way, but gives him a vulnerability he did not have before; he developed intellect on three separate occasions, for instance, and the first time it caused him to feel fear, leading to his defeat; the second time he decided he did not want to fight at all; and the third time it made him into 'Doomslayer', a being who made it his life's purpose to destroy all versions of Doomsday that existed. But survival is stronger, so his intelligence faded over time to turn him back into a nearly unstoppable killing machine.
He eventually evolved into something so lethal it killed all life in its vicinity, just by being there. When Superman destroyed him and absorbed his remains, he then started to turn into a new version of Doomsday.
To be honest I think Archanfel is the underdog here.