What it does
Thunder Punch is a physical Electric-type move with a paralysis chance on hit. Paralysis in Champions has a trimmed full-stop rate, so don't plan around triggering it — treat it as a bonus whenever it procs. The move is contact-classified, which matters for two reasons: Iron Fist boosts it, and Rocky Helmet/Rough Skin will punish it.
In doubles, it's a single-target move. Electric typing gives it neutral-to-supereffective coverage on Water- and Flying-types that frequently appear as support Pokémon, making it a natural coverage pick for Fighting-type physical attackers who otherwise can't threaten those types.
Who runs it
Medicham is the most dangerous Thunder Punch user in the pool. Pure Power doubles its effective Attack — the actual damage output is far beyond what its base stat suggests. Running the Fire/Ice/Thunder Punch combination covers such a wide range of types that no single Pokémon can wall all three. That breadth is the whole point of the triple-punch set.
Conkeldurr gets Iron Fist bonus on the move. As a slow Fighting-type, it often appears in Trick Room environments, and Thunder Punch gives it reach against Water-type and Flying-type partners it wouldn't otherwise threaten.
Rampardos has raw Attack well above most Pokémon in the format. Thunder Punch from it is a genuine KO threat on anything with Electric weakness — opponents can't just sit in front of it.
Crabominable (Ice/Fighting) uses Thunder Punch for Water-type coverage, typically in Trick Room builds where its low speed is an asset.
Meowscarada occasionally uses it for Water/Flying coverage, though its primary coverage usually runs Grass/Dark.
How to use it
The move selection is mostly a team-building decision: does this Pokémon need an Electric-type hit to cover targets it otherwise can't reach? If yes, Thunder Punch is the standard physical option.
For Medicham, the triple-punch combination forces the opponent to bring three different resistant Pokémon to wall all three hits — which is structurally impossible in doubles where only two Pokémon are active at once. The value isn't that any individual punch hits hard; it's that the combination is impossible to fully wall.
Tips & strategy
Paralysis is a bonus, not a plan. In Champions where full-stop rates are reduced, trying to fish for Paralysis with Thunder Punch isn't a reliable strategy. Use it for the Electric-type damage; anything else is upside.
Contact means exposure to Rocky Helmet and Rough Skin/Iron Barbs. Note opponents that carry these before clicking Thunder Punch into them — the recoil adds up over a match.
Iron Fist is the key differentiator. On Pokémon that have it, Thunder Punch is noticeably stronger than other Electric coverage options at the same slot cost. On Pokémon without it, the comparison is closer and other options may win.