I'm so dumb.
I had the first 3 pellets down, went to get the last one, and the ghosts were lined up perfect, but I forgot that I had eaten all the regular pellets, and when I went to chase, I ended up finishing the level instead.
I haven't wanted to throw my controller so bad in years.
Still haven't unlocked this achievement. The AI on these ghosts, is downright brutal. I wonder if I just got a bad copy 8P