Enhanced Body
Thanks to an experimental serum given to him while he was in the US Army, Slade Wilson's physical attributes are all at near-superhuman levels. He can outrun Olympians, dodge bullets like they were traveling through molasses, lift a car off the ground with ease, see farther, hear better, smell better… every aspect of his physical capabilities has been boosted to the limits of what the human body is capable of doing. He is also more durable than the average person by far, mostly to keep his enhanced body from ripping itself apart doing the crazy feats it's capable of doing.
Enhanced Mind
After being given an experimental drug by the US Army, Slade Wilson's mind was enhanced to a superhuman level. Consider his brain a computer with an infinite hard drive. Anything he sees or reads, he can recall in perfect detail. He can make calculations faster than other people realize that calculations need to be made, giving him perfect timing, navigation, and other skills. Stress and fatigue do not hamper his ability to run through the thought process, and he is never in need of 'a moment to think.' He can map out a hundred battle plans by the time the other guy's realized that he should probably go for his gun. For the most part, problems aren't problems to him. The only competition a brain like his faces is from a genuine innate super-genius like Reed Richards or someone whose brain can work even faster, like the Flash.
Healing
The experimental serum that enhanced Deathstroke's mind and body also boosts his body's ability to heal. Too much damage can still kill him, and it's not powerful enough to do things like regrow his lost eye, but his body is capable of mending wounds much faster than a normal person. The effect also slows his aging and reduces his need for rest, keeping him in his physical prime for far longer than a normal person would experience.
Strategy
Slade Wilson's greatly enhanced mind gives him an seemingly superhuman capacity for planning. He's adept at looking at every angle of a situation and mapping out every possible outcome. Whether this situation is meeting a prospective client, staging a complicated break-in, or assassinating a foreign leader, Slade applies the same rigorous strategizing to everything in his life.
Combat
Slade Wilson was an elite soldier even BEFORE he had his mind and body enhanced to the limits of humanity. Since then, he has only gotten better. He soaks up new fighting styles like a sponge, and his cunning and deep knowledge of human anatomy makes any weapon a lethal one in his hands. He's the sort of guy who can go into battle by himself, against an army on the other side… and it's not immediately obvious which side would win.
Tracking
Slade Wilson is an expert hunter, both of game and men. He was accomplished even before experimental drugs boosted his abilities, but now he's truly elite. While his enhanced senses are not at the level of a figure like Wolverine, his greatly increased brainpower compensates, and he's able to track targets through all kinds of environments, even when they think they're hiding their trail.
Deception
Slade Wilson thinks faster than nearly anyone on the planet. This is great for fighting and plotting, but it's also really useful for 'reading' people. Don't play poker with him, he'll catch your tells on the first hand. Being able to read people so well also means that Slade is great at presenting himself in a way that seems favorable to them. He can disguise himself as someone else and infiltrate a secure facility, or he can convince someone that he's their best friend.
Stealth
Slade Wilson has trained himself to not be seen when he doesn't want to be seen. Whether he's creeping through an enemy base, or hiding in plain sight in the middle of a restaurant, he's excellent at blending in with his surroundings to get in and out without anyone noticing unless they're really, really looking for him.
Weaponry
Slade Wilson plans his missions down to the tiniest detail. One of the bigger details is arming himself. He has the contacts and the money to get virtually whatever kind of weapon he wants. Some are more difficult than others, like getting an AK-47 with a burned-off serial number compared to getting blueprints for a dirty bomb, but Slade works hard to make sure he's equipped with what he needs.
Gear
In addition to weapons, Slade Wilson pays close attention to what kind of gear he's equipped with otherwise. Much of this equipment is mission-specific, for example if he needs a recording device or some kind of specialized toolset for breaking into a specific security system. For the most part, his default is bulletproof combat armor and a helmet whose eyepiece has a built-in HUD for things like night vision, zoom, infrared, and so on.
Wealth
Slade Wilson is perhaps the highest-paid mercenary in the world. He does jobs that other crews think are impossible, and he knows exactly how much people are willing to pay for that. He's also hidden away much of this money around the world in various accounts, investments, holding companies, and similar things. Slade is not nearly one of the richest men on the planet, but it would take a concentrated effort to burn through his fortune in one lifetime.
Honorable
Slade Wilson is an honorable man, even if he sometimes commits dishonorable deeds for money. If you hire him, he will honor his contract. If you say it's a knife fight, he won't sneak in a gun. Slade is a man of his word, and can be held to it.
Loyal
If you make Deathstroke your ally, then you have an ally for life. Deathstroke is extremely difficult to make friends with… hell, he's difficult to become associates with, but to those who have put in the effort and made it through to the other side, Slade will risk his own life to defend the people who have his back. The flipside of this is that to betray him is to make an ENEMY for life…
Moral Code
Slade Wilson is a soldier of fortune, but he has standards. He doesn't target civilians, he doesn't kill children, he doesn't "punch down." He's totally willing to fight a superhero or the cops to see his mission through, but those are people who know what they signed up for. Slade will turn down missions and clients that he feels are not compatible with his moral standard. Sometimes this means leaving a LOT of money on the table, but Slade sees respecting himself as more important than any fee.
Cynical
Life has presented Slade with a lot of situations, and a lot of them have been pretty awful, like war zones. Slade has a tendency to assume the worst in people he doesn't know, and his view of humanity can often be a dim one.
Enemies
When your job is to fight and kill, you make enemies, and sometimes powerful ones. There are people who want Slade dead just as much as there are people who want to hire him.
One-Eyed
Slade Wilson lost his right eye during his time as a private military contractor, before he upped his game and became Deathstroke. His enhanced body has made his left eye able to compensate and avoid the loss of depth perception, but he's that much more susceptible to being sucker punched on his blind side.
Overconfidence
There are times when Slade is so sure that his plans are going to work out how they're supposed to that of course they go belly-up. No one can plan for sheer dumb luck, and situations like that can really open Slade up to taking some punishment. He's very adaptable, and will quickly come up with a Plan B, but that's still having to come up with a Plan B…
Vindictive
If you mess with Slade badly enough, he will do his best to end you. It takes serious work to reach this point, but if Slade is mad enough to declare someone an personal enemy, he will turn all of his attention and resources towards getting back at them until he's satisfied that he's repaid them for their transgression.
Wrath
Slade Wilson is a master tactician and this and that, but there are times when he really loses his cool. This is a rarity, but it can happen: someone can piss Slade off to the point where he throws away tactics, throws away strategy, and just goes berzerk and tries to beat the hell out of anything in his way. Considering his fighting skills, this can make him even more dangerous in some situations.
