While XP is something we have got plenty of, credits are the real strong suit. We all have jetpacks, three thermal detonators, and various other gernades, one player has a fletchite launcher, a personal stealth field, heavy battle armor, and a sniper rifle, one player has a carbine, heavy battle armor, and a flamethrower, and one has an HOB Heavy Repeating Blaster and powered armor. The battles are so quick that the tension only lasts for like, two rounds max.

Or, start throwing enemies at them which are using armored speeders with auto-blaster cannons. That whole ten-to-one thing of what happens when ship-mounted weapons are used on personal-scale targets can go both ways….

Yeah, there's no limit to Adversary. You can make the difficulty to hit pretty much whatever you want.

However, anything past Adversary 3 or 4 is (IMO) a little on the ridiculous side, unless you're actually talking about Darth Vader or someone with that kind of power and in-universe clout.

Like Krieger suggested, I'd start with Soak, WT and ST. Bump up the numbers just a little bit.

The Inquisitor creation tool in F&D will let GMs whip up some pretty hard hittin dudes.

I can't remember if this has been discussed, but here is a great idea for boss fights:

http://angrydm.com/2010/04/the-dd-boss-fight-part-1/

Essentially, you create multiple phases for the fight. When your players defeat the first phase, you bring the second phase into play, which has more power and different strategies. Then when they defeat that, you bring the third phase into play.

At the end of each phase, the NPC would retreat and recover themselves. The next time they meet the PCs, they're a little stronger.

My suggestion would be to put them in situations where their awesome combat skills don't help. My group has 2 or 3 characters that are combat monsters, capable of dealing out staggering amounts of damage at range and in melee. It's hilarious to put them in social situations where all of that firepower can't help them and watch them struggle because of the way they built their characters. They've learned that there are definite penalties to ignoring the "social" side of things in my games and you either get to end up being someone's patsy or looking like a stuttering fool to the major movers and shakers they run into.