This is something I always get in arguments about, whenever I use the word tankie hexbear and grad users argue that its just a term for socialists.
I’ve always just used it to referr to authoritarian communists, i.e, people who unironically support modern russia, and/or oppose ukraine, and think nothing happened to the uyghurs.
Authoritarian left who think the end justifies the means. They’re willing to use extreme systematic violence to achieve a communist society.