Garen vs Gragas Top Matchup

Why Garen is favored

Decisive Strike(Q) clears Barrel Roll(Q)'s slow, and Perseverance(P) lets Garen recover when he disengages. A Diamond Gragas one-trick describes Garen's sustain as stronger and his Q/W as difficult to answer, which matches the matchup's Garen-favored result.

How to play as Garen

Use Garen Q to clear Gragas Q's slow when you need to move in, but account for Gragas E before committing to a close-range trade.

Garen Q removes the slow from Gragas Q, so it can clear the cask's slow when Garen needs to close distance.

Perseverance(P) restores health after Garen avoids recent damage, while Happy Hour(P) heals Gragas after he casts a skill; their sustain windows differ between trades.

Courage(W) gives Garen a shield and damage reduction that can blunt Gragas's spell damage during a trade.

How to play as Gragas

Place Gragas Q and let Garen spend Garen Q before triggering the cask; the recast slow then cannot be cleansed by that same Q.

Keep Gragas E to peel Garen's approach or spin instead of using it into Garen Q; if Garen starts Judgment, Gragas R can knock him away before you re-engage after the spin.

Sources

These notes come from r/GragasMains and r/GarenMains, checked against the champions' abilities.