It's time for matchup-specific ko's
The players seem to universally enjoy the matchup-specific call outs. It's a neat little interaction/easter egg. Now, you should take the next step.
Introducing Sandman gave you a really obv door. Remember when I told you that you should have snapped the players' rosters by half in coordination with the movie and let them win it all back over x time? Yeah this is one of those times. Kinda like bg's, gifting, and incursions. Gold mines and necessary fixes. Anyway, back to it.
Defeat sandman with an incinerate champ? He turns to glass and they shatter him. Use Attuma or Namor? Wash him away. But it only procs when the correct finishing blow/effect happens.
Obv sandman is a very basic one. There are tons of other non-fatalities (wink wink) that can be done. Which, I can't even lie here... I'm blown away that THIS company hasn't already seen the sales potential for this stuff. There could be diff ko's available with various input combos, they could be unlockable, they could be a prize to the top x% in y content. More than that, they could be equippable for war and bg defenders. Most players scoffed at the emotes, and rightfully so. Many probably still bought them bc we're addicts but that's beside the point. Do you realize how crazy people would go for doom ripping out spines?!?! (yes I know that's not happening but you get the idea).
I told myself no more freebies a few years back but I like to see good ideas come to life. You don't even have to wait 6 months to start implementing this time. Players would love it and you'd get to pay real homage to your creators' fav comic memories. Revenue thru the roof, players, enjoying things, and nobody had to take anything from players to make it happen.