Universe with no Rassilon

"I have seen a universe where there was no Rassilon, and the Time Lords were gods thanks to me."

- Omega.

In one of the palimpsest universes observed by Omega, there was no Rassilon and the Time Lords became "gods" thanks to Omega alone. Omega told the Infinity Doctor of this, clarifying that what he saw was, rather than a parallel universe, a version of his own reality. (PROSE: The Infinity Doctors)

Relation to other realities
During the First Omega Crisis, Omega insisted that without him there would be no time travel and that the now Time Lords would still be locked within their own time. Up to this incident, the Third Doctor acknowledged Omega as his greatest hero. (TV: The Three Doctors)