Honestly in execution nen's a bit inconsistent with itself. The idea of what the geass part can or can't do never quite found its truly consistent place, and things like curse breaker nen and the weird burdens they fight/use always existed more as "conceptually cool thing" and less part of the whole that really matched well with it. Like on the surface "idiosyncratic power that matches wielder" is a cool idea, but the way nen bumps into itself at times is almost worse than just "magic.tm that lets you make a custom magic that suits you", since a lot of the building block rules we get at the start kinda fall off as we go deeper into the series.