While he is resting after his attack run your hero behind him to the other side of the screen so he has to walk there and while hes walking have a fast titan attacking him while maybe golems holding off anything that spawn.
Its a good idea to have the 3 titans that you can get so far here (death from extra 7,white tiger from killing 5000 units and golem(s) for geting all of the hero's upgrades)and a unit that knows shield and one with regen.Use the shield when inferno gets close and run past him and heal after that. Also,keep one of the titans (i used death)at the end to kill any units spawning.So when you get there, they don't just end up killing the hero.Keep doing this til you kill inferno. Now,can some1 help me with Colossus.Beat everything but him