The ability to go into a mode made for combat. Variation of Mode Switching.
The user can go into a mode or form made for combat, increasing all the combat skills (including attack, defense, etc.) and powers of the user to their apex, and possibly grant to them new powers required for the combat.
Users of the Abomination class (Darkest Dungeon); can turn into a beast with more damage and resilient to venom through Transform.
Chief Moginaian (Dragon Ball Super)
Wahl Icht (Fairy Tail)
Panther Lily (Fairy Tail)
Ikaros (Heavens Lost Property)
Sora (Kingdom Hearts)
Kuyou (Rosario + Vampire)
Tony Tony Chopper (One Piece)
Mihkail (Steel Angel Kurumi); via activating her Mark-II Angel Heart
Android (Valkyrie Crusade)
Trigger Users (World Trigger)
Kolulu (Zatch Bell!)
The TwinTails (Gonna be the Twin-Tail)
Undyne (Undertale); as Undyne the Undying
The Iron Giant (The Iron Giant)
When Kei and Yumi (Ape Escape 3) morph into the Dragon Kung Fu Fighter, they become specialized in hand to hand combat. They are able to attack multiple enemies and boost their strength for more powerful strikes.
Chief Moginaian (Dragon Ball Super) in his Battle Mode.
Kuyou (Rosario + Vampire) in his Ultimate Battle Form.
Wahl Icht (Fairy Tail) when he enters Assault Mode, transforms both his physical appearance and personality into a metallic fighting machine.
Ikaros (Heavens Lost Property) using her Uranus Queen Mode in order to defeat Chaos.
Sora's (Kingdom Hearts) Valor Form is specifically geared towards physical combat.
Tony Tony Chopper (One Piece) in his Kung Fu Point.