Im pretty sure that everyone agrees Sabertooth can kill anyone he can reach, but his inability to travel at any speed beyond a fast jog means he's completely unthreatening to a Galactic Empire. He murders everyone on one Death Star, or one Star Destroyer. Then it is a drifting hulk, which he has no idea how to pilot, and he spends the next 10,000 years drifting through space on his way to another star system. The remaining 900 billion people in the universe remain unaware of his existence.