Alright, so, skill
So, heads up, this is going to be involving a hell of a lot of cross scaling with Trigun. But since Ginsama was the Trigun person of this whole forum and wiki, I'm gonna take his words that they both exist in the same world
Skill
So first up, Grave has some bonkers skill. At the very least, Grave (or Brandon Heat, his living name) scales above Eye of Michael members at the very least. These members are able to predict everything about the person, ranging from their skills, moves, habits, and more. Further, these members can even fight against Vash the Stampede himself, though not for long. Grave can even scale to higher end Eye of Michael members such as Wolfwood and Livio, with Livio here being important. Livio has "2 layers" (dont know how that works) of analytical prediction, and after controlling Razlo his secondary personality he was able to keep up with an opponent vastly faster that has their own speed amps, who has a passive that can only be described as "an anti-skill aura", and Livio still beat this person with skill, which is what Gin was trying to get across, I think.
Grave's own gunplay shouldn't be scoffed at either. In his earlier days as a sweeper for Millenion, Grave was shown to be able to casually pick up a sniper rifle, before CASUALLY just picking out a spot to shoot at and pulling the trigger. This spot was where the target was somehow. This is even more impressive, because the target was behind a curtain obscuring who they could even be, from multiple building lengths away, all without even the slightest hint of prior knowledge because he just entered the sniper room where Bunji was and just knew instantly where the target was. Also going back to his younger days in Millenion, even when he was going up against Blood War and forced to fight off multiple immortal Deadmen, Brandon was able to stall off these Deadmen while barely getting hit throughout while constantly damaging himself while using a hand-canon of a gun, enough so that more Millenion members arrived. Not to mention in the games, Grave has fought more Deadmen such as a revived Bunji, Sherry Walken-MacDowell, and the terrifying Fangoram. And while not on the level of these 3 nor a Deadman himself, Zell Condorbrave is an equally impressive opponent, being a mercenary commander and having his squad hired by Corision to hold off Grave because of his skills in taking down Deadmen.
And now that I'm finished with this, I should mention that Grave likely won't hold back in the slightest as Mika isn't here.
Attacks and Powers
Here's the meat and potatoes if the skill section wasn't already that part. Starting off, Grave already has a large arsenal of weapons, most of them stored in the Death Hauler. There's the Ceberus handguns, Grave wielding the left and right heads. And with the Death Hauler, it contains a myriad of weapons, such as a gatling gun, multiple types of rockets that can home in, and what appears to be A DAMN RAILGUN. Grave has a good regeneration factor as well, being able to soak up bullets on the daily and regenerate nigh instantly. Now, the best part of his attacks are his demolition shots, his most powerful attacks which don't seem to have a limit on how much they can be used. You see that perception manipulation part on Grave's profile? Yeah, that's gonna play a huge part here. Anytime Grave uses a DS, it will kick in, which basically slows down time to anyone around to a near halt while Grave sends out an absurd amount of attacks. This is applied further with the Dawn of the Grave DS line, where Grave goes under the same time slow effect, but he moves around during it. It might look like he's effected slightly during this as well during game play videos, but I'm pretty sure that's just the PS2 breaking down lmao.
(Ignore Bunji there)
(watch till 2:25)
As you can see in the first video, Grave isn't afraid to spam these Demolition Shots one after the other. Resulting in an Overkill Execution.
Alright, I think that covers all. I would use G.O.R.E stuff but uhh, the profile is stuck in the Overdose days. I would also like to say that Grave, through sheer willpower can also get up after some time AFTER having been blown open by Fangoram's center-head, having his blood outside of his body, the same stuff that's supposed to keep him running. And after this Grave fared far better against Famgoram in their second fight, ie not getting one shot. The same thing basically happens against Who Knows Who in GORE, where Grave got his ass kicked before awakening again and being more powerful to the point he kicks WKW's ass. So this very much seems like Reactive Evolution or Accelerated Development, whatever it is, but I'm not sure about using this since it isn't in the abilities section.
Anyways, cheers, listen to the Gungrave Anime Ending while looking over this