Which Super Smash tech (wavedashing, L-cancelling, etc.) was the hardest for you to learn?

[killamch89]

From my perspective, wavedashing took weeks to nail, but L-cancelling felt intuitive after practice. Which advanced tech in Super Smash Bros. Melee or Ultimate frustrated you the most? Was it shield-dropping, dash-dancing with perfect pivots, or maybe the infinite combos with certain characters?