You're not saying anything about what kind of opposition the players faced, so it's a bit tricky to give specific advice. Here's the best I can come up with, though:
1) Don't use minions. When the players are packing that kind of hurt, it's time to make everyone at least a rival.
2) Assign defensive talents to NPCs. Adversary, Dodge, Side Step, Defensive Stance, Coordination Dodge, Heroic Resilience, and so on.
3) Give proper gear to NPCs. Let them have decent soak (5+) and at least 2 Ranged Defence.
4) Play the NPCs smart. In this case, have a melee-specced NPC get up close with the "problem character" and stick to him like glue. Use Pin, or a weapon with the Ensnare quality to prevent him from opening the distance and maul him to death with a vibro-axe.
I wholeheartedly disagree with this, expect 4 i merely disagree with the example.(Better just pepper them with stun grenades)
Increasing soak will only make the non repeater blaster wielders MORE useless.
And use MORE MINIONS break them down into mini squads of 4-5 and use 3-4 of them. And remember to space them out, put them out of short range (move to cover).
Same here! No to 1-2-3, 4 is mostly okay. Creating an arms race, in deed, makes the others even more useless. Making it more difficult for the Merc to hit makes it MORE implausible for anyone else to hit.
Besides, there's nothing Star Wars-like about heavy gunnery mowing down adversaries. No one one the movies won the day because they "tricked-out" their armor or weapons so that they were better than their adversary's stuff.
It also sounds like the encounters build up to combat at the climax, and that combat determines the outcome. It can, in some instances, but shouldn't always be. There's something to be said for using things like tactics, cover, ranks in adversary, better equipment, locations, and the like, but it'll will never overcome what a dedicated PC can do. In Episodes 4-5-6, the lightsaber battles weren't the end-all, be-all to how the story unfolded. In each movie they fought but there was more important things going on than striking the other guy down (Kenobi vanishing, "Luke, I am your father!", and I sense the good in you, father.) Nothing hinged on whether Luke could defeat Vader in combat.
Remember how the PC spent a lot of XP on their character. If they excel in combat, identify WHY they are so good. Does their 4-armed species aim a little longer than others? Have they inflated Agility or Brawn to high levels while ignoring a weaker characteristic? Do they have equipment better than their experience? etc....
As such, I think a good GM will find ways to reward the PC while balancing the encounters for everyone. PCs can and should shine in combat, especially given some specializations. Remove your own bias for a moment, and consider how you would enjoy play as another PC in the same game. Are you feeling robbed of the spotlight? Are there things for you to do that matter in the game? Does the combat monster show respect to other players, but just rolls really, really well?
Follow Order66 podvast's The List, and try to develop some encounters that use 'em. Share those ideas on the forums, here, and we'll help you. Start with #1....Make it LONG.
One simple thing is to have enemies on multiple sides. I don't care what the rules say, you really can't change fire arcs with a large weapon that easily. If you're in a bunker, blasting at everything in a 90° arc in front of you, great. If you're in a starship hallway, with stormtroopers coming at you from both ends, I'd only let you pick one direction to mow down.
This isn't D&D where the DM is god and out to kill the PCs. It's a game; the PCs are building their characters to perform how they want, and you are facilitating that development.
Let the combat monster roflstomp some minion groups onto the ground. I bet he loves it. Throw in some more so he can keep going.
Split the party if needed. If the others are feeling left out, have them go for the big bad while the combat monster holds off the mooks. Or, if they are built to do other stuff, write the other stuff into the encounter, either before, during, or after the combat scene.
Just make sure the Tech, the Pilot, the Medic, and the Face(you get the idea) have scenes where they, too can save the day. If the primary focus of your encounters is always combat, the ones having the most fun will be combat guys. I don't like the "penalize him by making him do other things" style in my games. Strongly encouraging your PCs through negative reinforcement is still basically railroading, even if it is just to make them build a character the way you want.
Tl:dr
This is a game, and everyone should be having fun. Different people have fun in different ways. Build encounters so everyone has fun, and you probably will too =)
This isn't D&D where the DM is god and out to kill the PCs. It's a game; the PCs are building their characters to perform how they want, and you are facilitating that development.
Let the combat monster roflstomp some minion groups onto the ground. I bet he loves it. Throw in some more so he can keep going.
Split the party if needed. If the others are feeling left out, have them go for the big bad while the combat monster holds off the mooks. Or, if they are built to do other stuff, write the other stuff into the encounter, either before, during, or after the combat scene.
Just make sure the Tech, the Pilot, the Medic, and the Face(you get the idea) have scenes where they, too can save the day. If the primary focus of your encounters is always combat, the ones having the most fun will be combat guys. I don't like the "penalize him by making him do other things" style in my games. Strongly encouraging your PCs through negative reinforcement is still basically railroading, even if it is just to make them build a character the way you want.
QFT.
IMO, It's always better to use positive encouragement than negative, and sometimes the line between those is blurry. If the combat monster is a problem, then remember "The supreme art of war is to subdue the enemy without fighting." Give other players a change to avert combats. Give Combat monster moments of shining in also other areas than combat. Try to make combat feel less rewarding for him than e.g. solving conflicts peacefully. Show Combat monster player other ways to solve situations. Don't force him to do anything.