Switcheroo

Choose two creatures that are different sizes. The creatures must make a Constitution Saving Throw, a creature can choose to fail this save. For the duration, you switch their sizes. For every size category above the target's original size they do an additional 1d4 on Weapon Attacks. For every size category below the target's original size they subtract 1d4 from their Weapon Attack. For instance, a Huge Creature turned Medium will subtract 2d4 from it's attack. A Medium Creature turned Huge will add 2d4.