DEATHDragon 4 Sep 2021 17:02

The first part of the fight is kinda tricky, you need to strike the pink sphere with Fire Storm while avoiding his arch shots. After beating the first form, get close to him, not too much, but enough to get almost under the cockpit of Wily's Machine. Then jump, fire, wait for the projectile and repeat. If you stay in that spot near the cockpit of the Wily Machine, the shot will go over your head, just don't get greedy with your shots. Patience is key.

TimeLink 28 Sep 2022 12:43

First Phase:
Attack with Fire Storm. Sometimes you can get up close and get hits with the shield to end the phase faster. Sometimes due to his backwards movement projectiles will also double-hit.
Generally you just want to weave around close to the Wily Machine. Don't hesitate, don't slow down. Just run back and forth, get a jump and shot in when you're on the left side. This phase goes down in 7 hits.

Be very careful with the phase transition! This is a little luck-based, as it locks up your controls and the projectile hitboxes are awkward. You can easily take a cheap hit here.

Second Phase:
Use Thunder Beam. It's not technically a weakness, but it double-hits most easily.
Run back and forth between under the Machine and about 4 tiles left of it. Jump, get a shot in, run back. Repeat. You always want to be dodging the projectile from below, staying under the Machine.

Reference Video: RoahmMythril's Perfect Run (Timestamped)
https://www.youtube.com/watch?v=rt8V5ZQG-Kw&t=213s