Here's why Absol can't sweep reliably, and shouldn't try. It's all about Sucker Punch. The best users of priority are Mega Lucario, Scizor, and Azumarill. Sucker Punch doesn't do much to them, and they OHKO back, without fail. These pokemon are EVERYWHERE. Against everything else, Absol absolutely has to OHKO or it's dead, because it can't take a hit from anything, really, and it can't hold a Focus Sash.
If you are going to dedicate a mega slot to Absol, you should coddle it and let it sit in the wings until it's needed. It's the best user of Magic Bounce in the game, and it should be treated as a check and counter to hazards and support pokemon; in tandem with your hazards, it can force switches and rack up damage. I won't deny that yes, it can smash down walls, but there are stronger, beefier wallbreakers in the game that don't use up a mega slot, so for the love of god use those instead and keep Absol alive doing what it does best.