Tigerstar wanted to be the leader so badly that he killed multiple Clanmates and led dogs to his old camp. He also led the dark forest cats against the Clans.
He blamed Yellowfang for killing some kits even though he did, he tried to steal kits, and he led the dark forest against the Clans.
Scourge was the leader of BloodClan, and took TIgerstar's lives in one strong swipe. That is kinda the only good thing he did. He tried to kick out the Clans and take over the forest but they ended up killing him. (Firestar killed him) So, yeah!