What it does
Slack Off restores the user's HP by 50% of its maximum in one action. No damage, no secondary effect — full stop.
In doubles, recovery moves carry a steep opportunity cost. The turn you use Slack Off, you deal zero damage while your opponents still get two attacks between them — one on each of your Pokémon. A wasted offensive turn in doubles can cost the game more directly than the HP it recovers. So Slack Off only makes sense when the Pokémon using it is so critical to the next several turns that keeping it alive outweighs the lost offense.
The question to ask before using it: can the opponents kill this Pokémon this turn regardless? If yes, recovering HP is pointless — the Pokémon dies next action. If no — if the Pokémon survives the hits and the recovered HP extends its effective life by several more turns — then Slack Off pays off.
Who runs it
Hippowdon uses it at 72%. Its role is to maintain Sand Stream — the longer it stays on the field, the more passive damage sandstorm deals. Slack Off serves the core tactic directly: keep Hippowdon alive longer. It's not an attacker; its value is presence.
Skeledirge (Fire/Ghost) has Unaware, which ignores stat boosts on the attacker. It walls boosted Pokémon while recovering HP — a combination that directly counters setup-heavy teams. In doubles, every turn Skeledirge spends on the field is a turn the opponent's boosted sweeper can't execute cleanly.
Slowbro occasionally uses it, primarily in singles contexts; in doubles its recovery usage drops significantly.
Bellibolt sometimes carries it to extend its presence as an Electric-type support attacker.
How to use it
In doubles: only use Slack Off when you've confirmed that your opponents cannot KO this Pokémon this turn, and the Pokémon is essential to a future turn that you cannot afford to lose it for.
For Hippowdon, the optimal Slack Off turn is when it's dropped to around 50% HP and the opponent's two attacks combined won't kill it — recovering brings it back to full and extends the sandstorm window significantly.
Tips & strategy
The cost is always the same: one offensive action. Whether it's worth it depends entirely on how valuable this Pokémon's continued presence is versus the damage your team misses out on this turn.
Unaware on Skeledirge creates a 'walling' interaction: setup moves do nothing to it, so the opponent can't boost their way past it. Add Slack Off, and they need to commit high-power hits just to remove it. That forces opponent resources toward a defensive problem instead of their offensive plan.