Raymond Hardnose
There are things from Raymond's time in the Army he doesn't discuss. The people who were there with him don't either. What came after that was a decision quiet, deliberate, and years in the making.
Now he runs Major Crimes. He knows something about everyone. Everyone owes him something. The power he's built isn't sitting on a shelf it's there so his team can move forward without looking over their shoulders.
Is he one of the good guys? Wrong question. If you're on the right side, he'll be there when it matters. If you're not, he won't come for you directly — things will just stop working out.
When the team hits a wall, Raymond removes the wall. How? Don't ask.