Heaviest .22 wadcutter is the Gamo Match at 15.43gr. Don’t waste your money on them though, they were some of the most abysmal pellets I’ve ever had the misfortune to try. Instead give the RWS Meisterkugeln a try. A perennially good pellet in most guns.
Assuming this question is in the same context as your earlier question about rats at short distance, a heavy weight offers no particular advantage anyway.