Memento is a Dark-type move introduced in generation III. It causes the user to faint and harshly reduces the oponent's Attack and Special Attack. To me, this seems like a very bad tradeoff. When I compare it with Explosion which has an effective power of 500 (officially 250, combined with halving the opponent's defense) or with Belly Drum which cuts HP in half and maximizes Attack, I can't help but feel like Memento is a completely useless move. Maybe it would be useful if it minimized Attack and Special Attack instead of just reducing both by two stages, but it doesn't do that.
What is the strategic value of Memento? In what situations is it genuinely useful?