As multiple people ITT have pointed out, cellular regeneration, organ regeneration, etc etc.
You're essentially immortal unless you throw yourself into a pit of lava.
...okay
sounds similar to attack on titan regeneration except not as good.
How does it work in AoT?
There are multiple ways regeneration can work even in a single universe, tho.but none of them that i'm aware of in dragonball (please note: i don't watch super nor do i consider it canon (subnote: i am aware it is canon, that does not mean i have to like it and i choose to instead live in the land of make-believe where it's not canon)) make you immortal.
While in human form, titans can regen as well, it's just slow and doesn't seem painful, though it does weaken them while regen is happening. I also think they can't turn titan again until completely regenned but I'm not 100% sure about that.
(please note: i don't watch super nor do i consider it canon (subnote: i am aware it is canon, that does not mean i have to like it and i choose to instead live in the land of make-believe where it's not canon))