Highly character- and scenario-dependent card, it can trivialise some enemies. Notable characters who can use it well would include Rogue and Cyclops, as they can consistently put upgrades on minions, though you can always help yourself with Air Cover.
It provides a very easy way to defeat minions like (the list is not exhaustive, just some examples to keep in mind):
Those who hinder your ability to attack or damage them:
-Blob 3.14 (who otherwise can only take 2 damage from each attack)
-Edison's Giant Robot (can't take damage until a resource is spent)
-Thomas Edison (can't take damage if you're engaged with other minions)
-Sebastian Shaw (can be attacked only once per phase, gets tough cards easily)
Those who simply have a lot of HP:
-Brothers Grimm (8HP)
-Badoon Headhunter and Headhunter's Henchman (7 and 8 HP respectively)
-Sentinel Mark VIII (8 HP)
-Tombstone (9HP)
Those who have nasty effects on being defeated or taking damage:
-Sandman (Iron Spider's Sinister Six, has you discard cards after getting damaged by an attack)
-Shifting Apparition (shuffles encounter cards into your deck if you defeat it with excess damage)
-Delgado (gives the villain a boost card and clears their stuns and confuses)
-Embassy Guard/Patrol (puts 1 threat on Batroc's Alert Level)
-Hydra Soldier (gives the engaged player an encounter card)
-Madame Masque (triggers The Hood's Foul Play ability)
-Zero (conditionally shuffles itself back into the deck)
-Orion (gets a tough status card after being damaged)