From what I remember of the Renegade Doctor, he said he could do stuff like eat the Sun and so on. Then again, that was Mark Millar being Mark Millar. He had Ultimate Loki saying stuff like he could bend the Universe to his will etc. So let's keep things in perspective and not start tossing them into the Skyfather tier or something. Classic Loki is just as much of a reality warper and has had his power compared to the likes of Dormammu and so on.
That being said, the Renegade Doctor erased dozens of alternate Wildstorm heroes (Majestic, Apollo, Jack copies etc.) easily which I view to be way beyond Loki's capabilities and something closer to Skyfather level.
BUT again, the very reason they were there to be owned in a single panel was because they were disposable, featless, alternate characters that are often treated as fodder.
So I guess I'll give it to the Doctor because his power level was implied to be beyond someone like Loki. Even though he didn't do anything Loki has not been able to accomplish as far as I remember and we already know a bootleg copy of Loki under Mark Millar got the same comments that will be the only thing Carver considers.
Man, that post was a lot longer then I expected.