He did many things from the expansion of the state to major reform to civil war. He also mentored his successor like a son which could be called his fault, good or bad.
You might wanna check out the FAQ on Julius Caesar because it has a bunch of answers about his life and impact including:
Why was Julius Caesar considered a Tyrant, and how exactly did he bring down the Republic? by /u/LegalAction and /u/XenophontheAthenian
Was Julius Caesar a reformist, a conservative, or just an opportunist?
Was Julius Caesar a good person in real life.
There's a lot of other answers on different aspects of his political and personal life but those are the ones that pertain to your specific question.