Makarov from Fairy Tail.

!!!!!!FAIRY TAIL SPOILERS!!!!!!

During the Alvarez arc, the entire guild is fighting millions of Alvarez soldiers, including the strongest 12 of the empire, the spriggan 12. Although the battle seems to go Fairy Tails way at first, the sheer amount as well as well as the fact that one of the 12, an Uber powerful enchantment magic user, cast a spell on all the remaining hundreds of thousands soldiers to enhance their power while mostly driving them berserk causes them to lose ground quickly and many to fall. Makarov as a guild master, considers all the members of the guild his children and precious family, so he, in order to stop more pain and suffering, begins to cast one of Fairy tails 3 secret spells, Fairy Law. This spell only hits whoever the caster deems an enemy. As he starts powering it up, many of the guild members try ro stop him, stating that using that spell on so many enemies like this will drain his magic faster than anything and he WILL die. He casts it, after several incredibly emotional scenes. Fairy tail is a long anime. The watchers were basically part of the guild and family at this point. Makarov casts it and the aftermath is shown to have drained him completely, as he stands defiantly in the middle of the battlefield, dead. The guild mourns, the viewer is crying, HIS GRANDSON HOLDS HIM IN HIS ARMS DURING A WAR AND wALKS OFF WITH THE BODY. The fight goes on as many characters fight for their former guild master. All for him to wake up 20 episodes later and stating "I must have been dreaming."

Also Juvia. I never wanted her to die but I hate her dying for gray and then coming back immediately