IS-4
The USSR’s IS-4 used to be a Tier 9 Heavy tank. Enough said. It used to have the IS-7 gun and would face off against Tier 5 tanks thanks to its matchmaking. This was at a time when there were only USA, USSR, and German tech trees, each extremely limited in their tank offerings.
Several people from the community claim the IS-4 was far better than the IS-7 at the time, which actually came after it at Tier 10. Now, instead of the mighty IS-4 sitting at Tier 9, it’s made its way into Tier 10—with its armor unchanged. That’s right, the armor it has now is the same as it was all those years ago. For those who've yet to sink their teeth into a good USSR tank line, the IS-4 can be found at the end of one of the best USSR tank lines in World of Tanks.