Mindless Hulk is the most destructive alter-ego of Hulk and as the name implies is completely unable to be reasoned with. This Hulk is even more violent and unpredictable than Savage Hulk and is infamous for being responsible for a massacre due to the evil influence of Nightmare.
While under the control of Mindless Hulk all sense of Banner is lost and the Hulk's intelligence is completely lost. However his rage is amplified to its maximum potential as Mindless Hulk is continually furious and willing to destroy anything in his path : friend or foe.
In this version of Hulk he caused massive amounts of destructing to the point he fought most of the Avengers before ultimately banished to the crossroads of dimensions by Doctor Strange. Due to a fail safe while Hulk could travel dimensions.
However he could only go to ones that he couldn't just overpower all sentient life in it and where he could survive since Stange didn't want to hurt Hulk. Anytime he became unsatified enough or in a world where he had next to no survival and nothing the fail safe returned him to the crossroads to find a better world.