Ori and the Blind Forest: Definitive Edition - Nintendo Switch

This is a video I made to show how to boost in order to get enough ability points for this achievement, especially if you're towards the end of the game.
It takes a while, though, and I was playing it on Hard mode.
Hope it helps...

There are a total of 33 Ability Cells around the world. Added to the experience you get from killing enemies, this should just be enough by the end of the game on Easy or Normal to unlock every ability tree upgrade and get Phenom (as well as Soul Master, Utility Master, and Combat Master). I do not advise going for these four achievements on Hard mode because it takes 75 ability upgrades to max out tree on hard, as opposed to only 54 upgrades on Easy or Normal.

The video below shows all collectibles in the game, including all 33 of the Ability cells to make netting these upgrade achievements easier.

This is a guide for quickly grinding experience in case you gathered all ability points already. At the top of the giant room in Valley of the Wind going into Sorrow Pass is a set of crows and above them are some bulbs you can kill attached to the ceiling. On the left of the bulbs is a little green guy that you can kill. Float up there and take them all out. I used Charge Flame on the crows and the bulbs but on the green guy I like to repeat stomp next to him to keep him stunned. Once you have cleared them, drop back down about half way or lower into the giant room and float back up. Most of the enemies should have respawned. Sometimes they even respawn while you're clearing them. If you take too much damage and need to heal you can drop to the bottom right side of the large room where a save point is and repeat the process.