Tyrant is the type of guy who can't help but make enemies. He's a power-addict, so at one point he was ruling galaxies all over the place. Honestly, I don't know how you'd do that. Sure, his castle was an entire planet, but that's still a lot of ground to cover if your people start acting up. He started wars with anyone he could, but he made the mistake of messing with Galactus. Galactus ended up killing him, but when you're as powerful as Tyrant, you don't go down with one swing (even if that swing destroyed you).
After that he took on people like Silver Surfer and even Thanos, who he beat. Thanos is stronger than Tyrant, so I don't know how he pulled that off. We all have bad days, I guess.