Short version? Mix and match the following:

• Pro Xi Jinping
• Pro Joseph Stalin
• Pro Mao
• Pro use of tanks against civilians as in Tiananmen Square in 1989 or Hungary in 1956.
• Pro Vladimir Putin

Basically a tankie is any apologists for government violence against civilians -- usually by claiming something like, "those weren't real civilians. That was a color revolution. The government of [authoritarian regime] responded with no more than the necessary amount of force. Western propaganda is making it look more violent than it was in reality."

From Wikipedia

The term "tankie" was originally used by dissident Marxist–Leninists to describe members of the Communist Party of Great Britain (CPGB) who followed the party line of the Communist Party of the Soviet Union (CPSU). Specifically, it was used to distinguish party members who spoke out in defense of the Soviet use of tanks to crush the Hungarian Revolution of 1956 and the 1968 Prague Spring uprising, or who more broadly adhered to pro-Soviet positions.

the leftist equivalent of an alt-right person i guess

Yeah if they're banned then they'll go back to their bubble saying they're being silenced, but how can you silence someone who's not contributing to the conversation?... I'm fine with different opinions, but I don't understand people who think the way to convince someone of your viewpoint is hostility. Telling someone to "fuck off" with no reason is just toxic. Once might be a bad mood/state of mind (happens to the best of us), but repeat offenders shouldn't be allowed to keep harassing others.