This is a twofer. By that I mean;
The requirements for this achievement are 80 challenges. Doable solo across 25-30 matches, 80 is the easy grind for any character (compared to the 150). Having a second controller, or going 1-10 in survival makes it easier/faster.
However, as of writing this, "Competitive General RAAM" is glitched. That happens to be a cheevo for your first ranked multiplayer victory, and will only unlock when this, the 80 challenges, are completed. Excluding Omen, who has no ranked achievements, RAAM is the only character who can't unlock "Competitive _____" the usual route.
This is a mixed blessing, depending on your skill an patience with him, and your usual luck with ranked.