Is one core exercise enough?

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Would have put this in my last thread but it got a bit bogged down so thought I'd start a new one

Realized today my work is starting to bear fruit, looking a lot slimmer and starting to see some definition, but I've still got a lot of work to do. At the moment a lot of my work is being done on a set of rock rings, but plan to build a fingerboard soon to start working the fingers harder.

The main exercise for my core is the l-hang or hanging leg raise if I understand chillen correctly. I'll let metolius describe it better then me.

L-Hang: The emphasis here is on core strength. Choose a hold that you're fairly comfortable on. You can dead hang or bent arm hang. Pull your legs up from the hips, keeping your knees straight and your toes pointed. Hold a static contraction with your legs at 90 degrees to your torso or do slow repetitions raising your legs as far as you can but only lowering to about 45 below horizontal. If you lower you legs all the way, it will take the tension off your abs and constitute a rest. The idea is to keep your abdominal muscles contracted the entire time.

Three reps of 20 seconds of this seems to wipe me out, but was wondering as its a static exercise if I should incoporate another exercise. If so what should I add? Ideally it would be another one which wipes out the muscle group fast and requires minimal equipment so I can do them at home.