Users become stronger, faster, more durable, etc. by hope of oneself and others, possibly unlocking abilities related to the affinity and enhancing the existing powers. Some users may be able draw sustenance from the hope or even slow or stop aging.
Gerard Valkyrie (Bleach) gains strength based on miracles manifested from the hopes, fears, feelings, and desires of the masses. His allies' hopes allowed him to manifest them into a nigh-unbreakable sword.
Joshua Christopher (Chrono Crusade) is the Apostle of Hope with an ability to heal others that is in direct correlation to how many people are displaying great hope in their own selves.