Since you can't do this for the quest, I figured I'd just give you my own anecdote. I did Ace because 1) I love the gun (Fatebringer was my fave in D1) and 2) for canon reasons I wanted to do it (for Cayde). I [i]hate[/i] Crucible, and only occasionally play to get my milestones. I'm not a fan of the playstyle (fast and hectic, as opposed to the more methodical and strategic PvE), and as such, I suck at killing human opponents. The only decent hand cannon I had was Ikelos, so high rate of fire, low power. You just have to resign yourself to the fact that you're going to die a lot. Try to swoop in when opponents are distracted, try to be outside their range when you first attack (sometimes you'll be facing other people with better hand cannons, and you're probably screwed then). Be patient, realize that you're going to have to spend a few hours playing Crucible. You don't have to get 25 in one match, you just have to get 25, so even if it takes you 50, or god forbid 100 matches, you'll still get it. As you progress you'll get more and more headshots per game, so it'll go faster than you thought. Good luck! I promise that the hardest part of this quest is the mental block that people like you and I have when going into the Crucible. You'll get it done.