I believe it is full ap, spirit visage (heal buffs) gp w... by going full ap you get around 800 hp back on his oranges.. add spirit visage and ardent censor (?) it may be the greatest? and i mean burst not continuous .. (If you're gonna try match it dont say scenarios that are impossible in a norm game).
It has to be burst/single target
Soraka's ult when an ally is under 40% health. It heals 525(+82.5% AP). With full ap that's over 1000 healing on potentially all allied champions, including yourself.
The best single target instant "heal" is Lulu's ult. 600(+50% AP) Although you get the most health out of Zilean's ult if you get to use it. 1100(+200% AP)
If you sufficiently restrict your judging criteria to the specific scenario under which Oranges excels, then Oranges is the best heal in the game.
If you use different judging criteria, a different ability will be superior.
I like how the OP aska a question then argues with everyone that answers him.
Voli can can get over 1000 HP back from passive heal if you build health.
Mundo can 3/5 his health bar back with his ult.
Considering circumstances and whether or not it's considered a heal, wouldn't Ekko's ult be the best? Imagine full tank Ekko gets caught out 1v5 and takes 99% of his hp in four seconds before ulting...depending on the build that could be upwards of a four thousand hp instant heal.
425+150%
Heals for about a 1000 and you have 4000+ hp
