What it does
Double-Edge is a Normal-type physical move with among the highest base power in the Normal physical category. Every time it connects, the user takes 1/3 of the damage dealt as recoil. Deal 150 HP of damage — take 50 back. That math accumulates fast.
Normal-type coverage is broadly neutral — it hits almost everything for standard damage except Steel (resists), Rock (resists), and Ghost (immune). So Double-Edge is a general-purpose hit with no specific super-effective matchup, but also no easy wall.
Contact classification applies. Against Rocky Helmet or Rough Skin/Iron Barbs, the contact recoil stacks on top of the 1/3 self-recoil — HP drains extremely fast in those matchups.
Who runs it
Snorlax uses it at 27% usage. Extreme HP pool means recoil is proportionally less damaging. Thick Fat reduces Ice and Fire damage by half, so it survives longer in those matchups and can sustain a few Double-Edge uses without immediately crumbling.
Kangaskhan is the classic high-power Normal physical attacker, especially in Mega Evolution form. Parental Bond delivers multiple hits in one action — Double-Edge is a natural fit for its 'hit as hard as possible' role.
Leafeon carries it as a high-power physical fallback when Grass-type moves don't cover the target. Solid physical Attack with a reliable normal hit that doesn't require STAB to threaten.
Wyrdeer occasionally uses it as its primary Normal-type physical output.
How to use it
In doubles, Double-Edge is for Pokémon that aren't planning to stay long. One or two big hits and then potentially switched out or knocked out anyway. The recoil is acceptable when the Pokémon is going to take heavy hits regardless.
For Snorlax, the durability of its HP pool lets it use Double-Edge a few times before the recoil becomes a problem. The window for that is early in the match when HP is high — recoil from multiple uses when you're already at low HP finishes you faster than the opponents would.
In doubles, two opponents act per turn, so HP drops naturally faster than in singles. Recoil on top of that means planning how many hits you need and when to execute.
Tips & strategy
Life Orb + Double-Edge recoil stacks are usually too severe. Most Pokémon can't survive both consistently. If a Pokémon runs Life Orb, look for a move without self-damage instead.
Choice Band pairs well — the attack boost has no recoil, so Double-Edge at Choice Band power is a high-damage hit without the stacking problem. For burst-damage builds, that combination is near-maximum output.
Ghost types are immune to Normal. If the opponent has a Ghost-type on the field, don't click Double-Edge into it — it's a completely wasted turn in doubles.