Please consider extremely specific nerfs/buffs, such as different damage against champions/minions.

Lulu support was butchered because Riot didn't like Lulu top/mid. Her poke as support was cut by a staggering 30% if her target is behind a minion or another champion. Due to the trajectory and range of her Q, this is a massive damage nerf on her only real damaging ability (E is generally saved for shielding). This not only hurt Lane Lulu's waveclear, it hurt Lane Lulu and Support Lulu's damage against champions, resulting in a much larger lane nerf than expected and an unintentional nerf to Support Lulu. Now Lulu support is incredibly weak and Lulu lane is gone. She was seriously hurt as a champion.

This could have been avoided if Riot simply changed her Q to deal 70% damage to minions, tones down Lane Lulu's waveclear without reducing Lulu's damage against champions by a fraction.

Nautilus has had his damage decreased multiple times, usually because of his success as a support or laner. IIRC he was designed as a jungler, and his jungling was neutered because of those changes to damage.

This could have been avoided if Riot decreased the damage while providing a small amount of bonus damage to monsters. EX: E does 20% bonus damage to monster.

Point is, when champions have multiple roles, or are currently being used in an unintended way, instead of just killing the champion, have the tiniest bit of foresight and only change what you intend to change, instead of causing huge unintended consequences.