system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU] How many planets did Thanos destroyed/conquered/invaded successfully?

I only know that Earth was his last planet to destroy before the "time travel" and Captain Marvel said that there are only a few planets that could help an alien invasion like Thanos that's why she was roaming around planets. Hypothetically how many planets could Thanos have destroyed?
gpt
We don’t have a number but given how well various species know him - the Xandarians know about him and he has major alliances with Ronan and the Chutari. Plus he seems to recruit followers from childhood given we have Gamora and Nebula. 

I would say that he has been doing this for several decades at least.