There are a few mutants with regenerative abilities. The most famous being Wolverine and Deadpool...
So, if the X-men cinematic universe is considered, it is quite obvious that Deadpool is the better regenerator.
Is it true in comics too?
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Deadpool's healing factor is generally considered faster than Wolverine's but it also varies from writer to writer. In some comics Wolverine has regenerated from a skeleton and Deadpool has regenerated after being liquefied.
Also notable is the fact that Deadpool's healing factor is constantly battling his cancer as well as healing other wounds. If it weren't for his cancer his healing factor would go berserk causing growths and eventually killing him.
Reference: Marvel wiki on Deadpool's powers.