"There is no good or evil in light, or darkness. It does not exist. If there is justice in this world, it may well lie in love, and nothing else."
― August (Fairy Tail)
"I used to always cry and give up… I made many wrong turns… But you… You helped me find the right path… I always chased after you… I wanted to catch up to you… I wanted to walk beside you all the time… I just wanted to be with you… You changed me! Your smile is what saved me! That is why I'm not afraid to die protecting you! Because… I love you…"
Users become stronger, faster, more durable, etc. by love of oneself and others, possibly unlocking abilities related to the affinity and enhancing the existing powers. Some users may be able draw sustenance from love or even slow or stop aging.
Snow White/Mary Margaret Blanchard (Once Upon a Time)
Prince Charming/David Nolan (Once Upon a Time)
Jeremy Gilbert (The Vampire Diaries); maintains control over his urge to kill vampires through his love for Bonnie
Bilquis (American Gods)
Isolus (Doctor Who)
Diana/Wonder Woman (DC Extended Universe)
Holy ÄRM Aegis (Marchen Awakens Romance)
Crystal Heart (My Little Pony Friendship is Magic)
Star Sapphire (DC Comics)
Ian Stone (The Deaths of Ian Stone) unlike most Harvesters can feed of the love of humans rather then their pain or fear.
Being a servant of Mistress Love and Master Hate, Avatar (Marvel Comic) possesses various abilities because of that.
Tagamori Shinta (Gan-Kon) is able to draw on and be empowered with nearly limitless strength because of his love for Isana.
Brianne de Chateau/Ribrianne (Dragon Ball Super) can empower herself through the love and support of her allies.
Harry Griswold (Sgt. Kabukiman N.Y.P.D.) is powered by love, specifically the love of his mentor Lotus.
The legendary Holy ÄRM, Aegis (Marchen Awakens Romance) uses the power of the user’s heart as the source of its healing power. The more earnest feelings the user has for a specific person, the greater the power of Aegis’ healing is.
Yvaine (Stardust) is empowered by love to shine
Changelings (My Little Pony Friendship is Magic)
Freya Beauchamp's magic (Beauchamp Family Series) is empowered by love and passion.
Despite having betrayed Jesus, the Golden Tyrant/Judas Iscariot (Seikon no Qwaser) held tremendous love for his master, which drives his determination to resurrect Jesus Christ for two thousand years.