Can rancor repeatedly come back or is it a one time?
{rancor}
Every time the trigger happens.
It will bounce to your hand if goes to graveyard from the battlefield.
It does not bounce if it gets exiled, it does not bounce if it is discarded, it does not bounce if it is put into the graveyard from the library.
I'm a bit of a n00b. So thank you in advance for your patience.
As long as rancor leaves during battle it comes back to the player, this is infinite?
Yes
Yes, apart from what I have mentioned there is an exception.
If you cast rancor on a creature but your opponent makes it an invalid target (e.g. Kills it with {doom blade}), your rancor goes to the graveyard before it goes into the battlefield due to its target is not around anymore.
This will not activate rancor's trigger as it was not in the battlefield (I.e. it was still a spell)
Ty all