Well, Absol is honestly reeeeally frail. A powerful STAB or a super effective move can take it out no problem. Also, Burn cripples it. Absol's speed is also average at best, so it has to consistently rely on that Sucker Punch when it's in danger of being OHKOed. Either way, if you go for the 50% crit then you lose out on any other item, and it makes Sucker Punch weaker from lack of Life Orb or w.e. Also, your moveset is pretty fucking limited in your options, if you do choose to go Swords Dance, along with Sucker Punch and Night Slash, woah, you only have 1 moveslot left. If you don't go Swords Dance, your chance of sweeping is pretty much nil. If you don't go Night Slash, you're bait for Pokemon that can just status you, if you don't go Sucker Punch you'll get KOed immediately without accomplishing anything. Even with your crits, Fighting types still have a resistance to your dark moves, and Mach Punch isn't exactly reassuring for Absol. Assuming we are talking about which of the lower tiers should be in, and not its performance in OU, even if it's strong it's honestly far from a really dominant force.