Q: Is Cmaj13#11 one of the most complex chords?
A: that particular chord seems to me like a "ghost of the textbook". this chord appears in music textbooks but just doesn't seem to get used in the real world. so that's what distracts me from your question. also we have to consider the fact that just writing a chord symbol doesn't really specify how complex the chord is, because there can be a quite simple or complex version of almost any chord symbol