Simulating all transient solutions for RLC series circuits
As far as I can tell your simulations match what I get from this online tool. I only did the under-damped case and the tool only provides Vout across the capacitor but it looks very similar to your graph: -



Looking at the transient voltage peak I get an overshoot of 1.329 after about 5 seconds and this pretty much ties with your graph except yours peaks at 13.3 volts due to the transient step being 10 volts.


  What am I missing?


I don't know - they look good to me.