Risa

If you really want to get the full idea of what Kirk as a captain is like, dive into the old paperback novels. He has a presence of command that many good writers have expanded on, and there's a reason he's a legend among the many Starfleet commanders. Although I have a head canon that anyone getting to the point of captaining a starship has similar awesomeness in their character that can face just about anything head on. A 23rd/24th century version of the steely-eyed missile man.

Which puts a new light on the various captains in all the series that "failed" in some way. Decker and the rest. They were Kirk level, and what they went through still broke them.