I was reading an excellent post on evil overlords (should that be capitalized?) by James Spahn on Halfling's Luck.
I immediately thought, "I'd like to write something like that?" Then realized he had already written it. Okay. You can have your evil overlords. A lot of thought goes into them but what about the loyal lieutenant? There's a definite need for some background there.
While the evil overlord operates behind the scenes for a good portion of the game the faithful lieutenant is usually at or near the front lines, trading blows with the heroes in many cases. You have to work some stuff out for him. In many ways he is as important as the big bad. After all he gets the thankless job of implementing the big bad's latest plan and probably taking the blame for its failure.
Ask yourself the following:
Why are they following the evil side?
Maybe they don't know they are on the wrong side despite the black uniforms and faceless minions they command. They may have a good reason: patriotism, bringing order to the galaxy. Perhaps they are working their way up in command to where they are important enough to impose some sanity on the universe. Perhaps they are just waiting for the chance to shank the boss and run the whole show.
It's also possible the lieutenant, admiral, lord high executioner ... whatever is serving under duress. The overlord is sparing his family or his family. Perhaps they just don't see a way out. they served their twisted ideology long enough to see what it really is but know they have no escape. Surely the rebellion is doomed.
Maybe they are a mercenary sort working for the credits (lots of credits!) or some unobtainable artifact their master has promised them. Get enough bucks or the item they need and they'll switch sides ... maybe.
What is their function?
Their function is to make life impossible for the heroes. But there are different types of functionaries. A military officer will sic legions of troops on the good guys. A crime lord will use bounty hunters and assassins. The Master Torturer will wrest secrets from them or their dependents to use against them. The Mind Witch will turn them against each other. The Insidious Revenue Chief will track rebel funding and try to cut it off. Methods vary. The heroes' opponent doesn't have to be a trained killer ... they can lead trained killers or worse: auditors!
Why are they still alive?
Heroes, being heroes triumph a lot of the time. After a couple of fiascos in the field the Overlord is going to wonder why the lieutenant is still drawing a paycheck. Overlords are not the most forgiving of people traditionally. So why is your evil middle manager still drawing breath and not demoted?
Maybe the second in command got his job through relatives (a lot of kings and queens do.) Killing or removing them will cause problems so they get a few tries. Perhaps the lieutenant is a relative or child of the Overlord. Conquering the Universe is one thing, pissing off the spouse is another.
The Overlord might also be a realist. If a plan fails due to an unforeseen event it's not the commander's fault. The commander is the loyal lieutenant and above the pay grade where there is only one price to failure. Training a second in command takes a sizable investment after all. Killing them for no solid reason is just wasteful. Seriously if your field commander has had an unbroken record of success before these so called heroes showed up he should have a few chances to stop them. The replacement might do no better.
The second banana might be very good at deflecting blame onto others as well. This is a skill that is indispensable in an evil empire. A good manager always has a scapegoat waiting.
The second might be very useful in other ways. Yes the heroes triumphed again but General Brazzk did manage to put down another revolt in Sector 2814 and does keep the drug trade running smoothly.
Maybe the entire regime runs by the book. The field commander does too. If he fails it is due to the failings of his personnel or random chance because doctrine is infallible. As long as he follows the book he is safe.
Optionally the field commander is a governor of a large territory. Up to a point the heroes and rebellion is a local problem and may be handled with local forces. In fact the second in command will try very hard to keep the distant Overlord out of the loop to avoid sanctions.
Do they have an exit strategy?
The second may be willing to fight to the death. That solves everything. They may realize the regime is going down or that the Overlord will lead them to destruction prompting them to assassinate the boss of bosses or switch sides. They might even be willing to help the rebels but can you really trust them? Their exit strategy might be a fast ship loaded with credits and phony IDs. They may be slow on the get away and face the penalty for seven or so failures. Cue the third in command to take over! For the best of both worlds the second in command is set up to be cloned on demand. Let the heroes keep killing him, there's an unending supply. As they fail and are removed they can be upgraded!
Do they have any redeeming qualities?
They don't have to be all bad. They are presumably loyal or at least stay bought. They might have a sense of honor or even admire the heroes on some level and want to ring them into the fold after curing them of their misconceptions about the beloved leader. They might be pursuing a vicious campaign against genocidal aliens, slavers or pirates and be a defender of human lives (but not rights).
That special something.
Jaws had his teeth. Oddjob had a nasty hat. Victor von Doom had his intellect and drive. I forget the name of Ming's head robot but he was way beefier and armored than the rank and file robots. Vader had it all really. The lieutenant needs something special to make him stand out and give the player characters a run for their money. Ideally it should make the players say 'What the hell?" when first used. Maybe they have a one of a kind personal forcefield that makes most weapons useless against them. Maybe they are precog and can often see the heroes' next step (or dodge their blaster beams). Perhaps they are the latest clone and they know they can't die, just be uploaded. Perhaps they are among the last of their kind (race, creed, family) with powers long forgotten.
So don't overlook the loyal lieutenant. There's a reason they stand out from the faceless minions.