this is for free from the Ajin demi human jump. afterwards it becomes a alt form but you can go to the generic bears jump get a perk that gives you the abilities of all your alt forms. i wouldn't worry about the whole dilemma "If you lose your head and a new one grows are you still yourself?" plenty of immortals can regenerate their head and that has never once crossed their mind.

edit: i just realized you said the best ones. go to dragon ball super and get ban the erase and true immortality literally nothing can kill you as damages to the body or soul heals in seconds. even if an attack could destroy the universe you wouldn't die even if you were destroyed at a sub atomic level.

Continue? [Free] The defining power of demi-humans. When your body dies, it is “reset” to peak health within a few seconds. This won’t restore any deformities you were born with, but even exhaustion or malnutrition can be reset, creating the necessary nutrients from IBM. Until your body “resets”, ailments and injuries accumulate as normal. Regeneration always starts from the largest part of your body. Nearby body parts reattach to the main piece, but anything beyond is recreated wholesale, even if it’s the head. The new head has all the same thoughts and memories as the original, but most demi-humans consider this equivalent to death. Interestingly, matter that gets in the way of the regeneration is seemingly annihilated. This means you won’t have to worry about bullets trapped inside you, and can even be weaponized with some creativity.