Make an extreme buff then add a nerf to that buff to even it out
Examples: Malphites ult is now acrossmap. Although, the base damage is reduced to 100/150/200, and no longer scales on AP, only armor. Ashe's Ult splits into 3 different arrows when it hits an enemy champion. There is no longer a stun on her ult, and does not scale on ap anymore. Fiddlesticks's W is now a snare, and drains at the same time. It now costs 200 mana at max level, and the drain range is now 550. Sion's Ult is now infinite. Although, It does not scale with anything anymore, and when ulting, the enemy team has vision of you. Gragas's Ult splits into 5 different ones, and do 60% less damage per ult. Gragas's ult now costs 100/200/300 mana, and the range is 300 shorter.