I strongly dislike most comeback mechanics simply because I believe they're there more for the casual crowd.
That being said, while not perfect, I do think Tekken Tag Tournament 2's rage mechanics were done really well. There's more depth and options to it than just a super or an X-Factor that you can pop any time. Characters (depending on the team) get rage at certain points in their life bars, so it's not uncommon to see people end combos early in order to avoid putting the opponent's partner in rage mode. It can frustrate the opponent while also often keeping them one combo away from death, eliminating the threat of rage completely.
Another aspect I like about it is how it is related to your bigger Tag Assault combos. If you're going for max damage possible, you'll be giving your opponent rage often which works against you; therefor, it's important for you to manage your combos so that you can maximize damage in the most efficient way possible with one character. I think this helps put a bigger emphasis on the Oki game where a player will sacrifice damage for a reset, THEN attempt a big damage combo to cripple the other character; additionally, when a character earns rage, the mind games can change to focus on one player attempting to safely tag out and the other preparing to punish or prevent it.
And finally is the Tag Crash mechanic that I know isn't too popular. While most people don't like it, I enjoy how it adds another layer of depth to the rage system, allowing one player to burn his rage for a relatively safe tag out. It many cases it can be considered a victory for the player on the offense to be rid of the opponent's rage, so it often acts as an "Oki Breaker" ending the pressure in exchange for Rage damage. I think all these aspects of it make it more than a simple comeback mechanic and adds a lot of depth and strategy towards offense and defense, as well as managing not only your lifebars, but also your opponent's. It's not perfect, but I believe it works well.
Edit: I should also add that I prefer a rage mechanic that doesn't simply do damage like a super. With Rage, you have to at the very least, open up your opponent for a combo or successfully pressure and poke them to capitalize on it. It's not a single hitting move that suddenly levels the playing field. I prefer these mechanics over comeback supers.
