Unfortunately the OP and possibly co-worker would need to believe that the results of a CC analysis were meaningful. Also, some problems are irreducibly complex.

One solution is for the OP to come up with a shorter, cleaner, better, etc. solution. Actually presenting that version to the co-worker can be interpreted as directly confrontational ... though presenting metrics instead would more likely be interpreted as a side-handed attack, rather than a direct attack.

But if the OP can come up with better code, then that would answer to the OP's own satisfaction if the co-worker's code really is overly complex. Personal enlightenment (I tell this to myself) was all the OP was asking.