Use this card and target your own "Colossal Fighter". It will be destroyed by battle along with your opponent's monster, allowing you to Special Summon it back to the field and attack again in the same Battle Phase.
This strategy, and similar ones works with any monster that has an effet that activates upon being Destroyed by battle, as your opponent's monster is also destroyed and you get your monster's effect.
You can also use this card effectively with cards that "self-boost". This card makes their ATK equal to the opponent's and their own ATK boost pushes them above the opponent's ATK.
Use this card when you have a powered up King of the Skull Servants to equal its attack to an opponent's monster, suicide yours, then Special Summon another King from your graveyard to attack again, possibly directly for game.
This card works well with any monster that can attack your opponents lifepoints directly. Used in a Watt deck, normally low attack Watt monsters can attack with larger attack points.
Using this card while Wattkiwi is on the field can allow you to destroy one of your opponent's monsters without losing your own.