This achievement is very simple. All you need to do is win a game of Breach
as the ATTACKERS. Playing as the defenders won’t get you the achievement for some odd reason unless it’s an issue on my end.
Also, you can still earn the achievement if you join midgame and PvE works as well. As long as you
’re attacking and win the match, the achievement should pop.
Edit: Seems like the achievement will pop as well if you win as the defenders too. Achievement must’ve glitched out on me when I started
Edit 2: Seems like this achievement is a little wonky. First time I played Breach, I won the match as defenders and the achievement didn't pop until the second match where I won as attackers. My suggestion is to just keep playing until you get placed as attackers and win