The Monitor, when he died (killed by Harbinger) he created a netherverse and absorbed two universes away from clutches of the Anti-Monitor. Unfortunately in his haste to save the two universes and his energy to calm their populations his tuning machines weren't completed and the universes were merging into one, and would destroy each other.
So if killed by Tyrant, I don't think Tyrant will be around to brag about it for long.
At his peak/normal levels, Monitor was a multiversal power. It was only when Anti-Monitor went on his creation-busting rampage that Monitor's powers began to diminish.