Stoneborn Pact

"Your movement impairing effects effects mark enemy champions with an earthen rune that heals other allied champions who basic-attack them for 5 (+2.5% of your maximum health) over 2 seconds. The mark lasts 4 seconds."

They took off the part where the heal is reduced if you're ranged (presumably because they'd be building less health so the scaling would already make it lower) BUT this means that it does still work for ranged champions and the champion I know of that has the most consistent movement impairing effects is drumroll Ashe. Every auto would not only slow the enemy but also let your adc heal up attacking them. This presumably would work with the Forbidden Idol items which could put it at a 82.985 hp heal per auto plus the 20-35 health drain from ardent censor bringing it up to a potential 117.985 heal just from autoing the same enemy Ashe did. NOTE: this could even get bigger if ashe bought any items with health other than redemption.

Edit: Corrected my math its a potential 121.25925 heal with the above conditions