Colossal Fighter OTK

This OTK requires at least 4 cards. Somewhat unreliable, you need to make sure the opponent has a monster in attack position stronger than your Colossal Fighter, and some things to look out for are attack stoppers like Sakuretsu Armor and Mirror Force.

Cards to Use
Colossal Fighter, Rainbow Life, Fire Princess, Grinder Golem and/or Lava Golem

The first step is to have your Colossal Fighter and Fire Princess face-up on your side of the field (Colossal Fighter in Attack Position). Activate Rainbow Life. Now, since your opponent has a monster stronger than Colossal Fighter, attack the monster, and gain life points with Rainbow Life's ability instead of losing them. Then, Fire Princess's effect will activate, dealing 500 points of direct damage to your opponent. While being destroyed by battle, Colossal Fighter's ability can revive itself in attack position and attack the opponent's monster, therefore repeating the process above. You've won the duel after Fire Princess reduces the opponent's life points to zero. Grinder Golem is good to put in this deck. It is stronger than Colossal Fighter and the tokens he creates can be used for Colossal Fighter's Synchro Summon. It is best not to put Warrior monsters in this deck so that Colossal Fighter doesn't gain additional ATK when it goes to the graveyard.

Monsters

 * Colossal Fighter
 * Fire Princess
 * Lava Golem
 * Grinder Golem
 * Marauding Captain
 * Comrade Swordsman of Landstar
 * Five pieces of Exodia

Spell Cards

 * Double Summon
 * Reinforcement of the Army to get a Tuner monster out faster.
 * Any Spell/Trap removal card, for example Mystical Space Typhoon, or Dust Tornado

Trap Cards

 * Solemn Wishes

Cards to look out for

 * Cards that negate attacks, such as Magic Cylinder, or Mirror Force.
 * Cards that negate Special Summons, and Normal Summons,for example, Forced Back or Horn of Heaven
 * Cards that negate monster effects. for example Skill Drain.
 * Cards that negate trap cards, for example Jinzo or Royal Decree
 * Cards that negate spell cards, for example Horus the Black Flame Dragon LV8.