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.
Mihkail (Steel Angel Kurumi); via activating her Mark-II Angel Heart
Tuba Warrior (Memeology)
Undyne (Undertale); as Undyne the Undying
Android (Valkyrie Crusade)
Trigger Users (World Trigger)
Kolulu (Zatch Bell!)
The TwinTails (Gonna be the Twin-Tail)
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.
Wall Eehto (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.
Tuba Warrior (Memeology) can don his armour giving him a major increase in all his stats.