<world-building hat on>
Sure. Any powerful, emotionally-affecting, perspective-altering life event will do the trick.
<story-telling hat on>
A powerful, positive, emotional life-peak is great ways to end a character’s story, and most of the time we’re concerned with the spark event as the beginning of a planeswalker’s story arc. So storywise, it does more work for the character to be facing big, difficult problems they need to solve at the moment they become a planeswalker. Wrapping some trauma into their spark moment nicely propels them on a path of action, and connects their journey through their story with their nature as a planeswalker.
Maybe we could have a “Quantum Leap” or “Sliders” style planeswalker? All they want to do is get home to that positive situation, but their spark is uncontrollable. Maybe the next planeswalk will be the planeswalk home, but for now, let’s help out with this plane’s problems.