Injustice 2
75 Achievements
153-209h
Fire And Ice
Firestorm must defeat Captain Cold with the final hit coming from a Meter Burn Molten Trap
0.5%
How to unlock the Fire And Ice achievement in Injustice 2 - Definitive Guide
To do the needed 2 hit combo you need to press (if facing right), and right after the first flame hits your opponent feets, you need to press to do the Meter Burn thing. I'd recommend a jump distance from your enemy to make sure the first flame actually hits.
If done correctly, you'll see a second big flame on the floor (that's the second hit) that should kill your opponent.
edit: added some extra info
Happy Hunting
Select any mode you like, select Firestorm as your main character and Captain Cold as your rival. Select any map and start the match.
Once the match starts, keep hitting your rival until he has around 10% of health left in his red bar, make sure you have at least one boost bar filled. At this point, using Firestorm stay middle-close to your rival and perform this combo (having your rival to the right) (keep spamming ). If you see a quick white flash around Firestorm this means you have performed the Meter Burn correctly. Once your rival is defeated with the last hit of this combo, the match will end showing the trophy in the screen.
Video: https://www.youtube.com/watch?v=14Q9mg3hhLM. (Credits: HarryNinetyFour)
Finish the enemy off with the following combo: .