Gragas vs Lillia

Let Barrel Roll (Q) charge before detonating it: damage and slow grow the longer it sits on the ground, and if you don't recast it, it explodes on its own.

Drink Drunken Rage (W) before engaging: drinking takes 1 second, then you take less damage and your next auto hits every nearby enemy.

Engage with Body Slam (E) through a path without minions: you stop on the first enemy you meet, and hitting reduces its cooldown.

After Body Slam (E), cast Explosive Cask (R) behind your target: the blast knocks enemies away from the impact, sending them toward your team.

Against Blooming Blows (Q), stick to her or back out of range: only the outer edge of the zone adds true damage.

Get out of the center of Watch Out! Eep! (W): the zone deals much more damage there than at the edge.

Dodge her spells, even Swirlseed (E), which rolls to the first enemy: each one marks you for Lilting Lullaby (R), which puts every marked enemy to sleep.

If you have CC, use it on her: with no dash, she relies on the move speed Blooming Blows (Q) gives her for each spell that hits.