If they were being housed together the condition of the first gecko's feet is likely the result of being bullied by the other male. Males will either fight or one will dominate and beat up on the other. It looks like he has some scarring on his hips too--also likely from bites, which also more than likely caused the necrotic tail.
Just keep the feet clean and dry (if wet it can't scab over well) and make sure they shed okay until they clear up. He may have some issues with stuck shed on any raw, scabbed and/or healing areas until they are totally healed. If this is the case, soak the stuck shed and remove it carefully with a wet q-tip. You want to remove old skin, but not scabs if possible. Some stuck shed on top of the feet is okay if it is due to scabbed over areas, as long as it does not constrict the toes.
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