The Power of Love is a sword Scott Pilgrim unlocks in volume 4 book after confessing his love for Ramona Flowers, causing him to level up. During this same level up, Scott also received Guts +2, Heart +3, Smarts +1, and Will +1. The sword counts as a longsword, for which Scott chose as a proficiency back in grade 5 over the skateboard proficiency. He uses the sword to defeat Roxie Richter in a single strike.
In Scott Pilgrim's Finest Hour, Gideon steals the Power of Love from Scott, causing him to level down, then impales him upon it, killing him. He later uses it to stab Ramona as she tries to escape the battle using Subspace. Within Subspace, he tries to kill Scott again, but Ramona deflects his attack with her Subspace Suitcase, destroying the suitcase and regaining the sword along with it. Ramona then takes up the Power of Love (having been healed by acquiring it), and she and Scott defeat Gideon together with an X-Strike.
In vs. the World
The Power of Love retains its basic shape and a proper tang, but lacks the heart at the base of the hilt. However, it still retains its flame. Unlike the graphic novel, the Power of Love is not wielded by Ramona and breaks during the fight with Gideon. After Scott gets killed by Gideon Graves and uses his Extra Life, instead of getting The Power of Understanding he gets the Power of Self-Respect. The stats for the Power of Love in the movie are Guts +3, Heart +2, Smarts +4, and Will +4.
In the Game
In Scott Pilgrim vs. the World: The Game the Power of Love can be used as a weapon in World 7-2, but a cheat (Square, Square, Square, X, Circle, X, Triangle, Triangle or X, X, X, A, B, A, Y, Y) can allow you use it in any level against any enemy. The sword lacks the fire like in the comic and movie, but can send out an energy slice with every swipe. It can be knocked out of your hands and picked up by enemies for their own use. The sword can break, but it takes a long time to do so. Neither the Power of Understanding nor the Power of Self-Respect appear in the game.
Originally, the Power of Love was going to have a completely different design, looking somewhat like a cross between the book and movie versions. It also appears that the Power of Love wasn't going to be a weapon, but as part of one of Scott's attacks.