He is an intellectual genius, best-selling novelist, peerless mob boss, ruthless assassin, and top-tier streetlevel combatant.
Intellectual genius and best-selling novelist:
When he was four, he had memorized the phone book for several counties; at six, he could quote every line of Shakespeare; at eight, he had written numerous plays, short stories, and novels.
He wrote his first best-selling novel before he was 18. He continued to write several others before his death (around his mid-twenties).
He has a mutation that allows him to use more of his brain than usual, thus thinking far more quickly and comprehensively than normal humans, essentially like Deathstroke. He has almost total recall.
He is able to learn new skills very quickly, which is likely due to his brain mutation. This ability is sort of like Taskmaster, but not as efficiently or quickly---I've never seen him watch someone fight and then be able to immediately copy that fighting style, for instance. But on the other hand this is how he was able to learn fencing at a world-class level very quickly. (More on this below.)
His genius includes tactics: using the Riddler’s persona as a disguise, Rose successfully matched wits with Batman, in a crossover that is canonical with the Grendel universe, leading him through a series of clues and traps.
Mob boss and assassin:
He started working as an assassin before he was 18 and quickly became the top assassin in New York, after easily killing his predecessor.
However this was too easy and he decided to take over all of the crime in the city. He quickly did so and essentially became the Kingpin of his universe. Then he spread his influence wider, taking over all crime on the eastern seaboard, outdoing even the Kingpin's achievements.
In order to do this, he had his minions kill 23 mob bosses across the east coast, in a masterly display of planning and power. Here is a brief selection from this action:
After that, he had essentially no rivals as the head of crime on the east coast.
Grendel is extremely fast, agile, skilled, and accurate.
He is very skilled:
He rarely fails anything that he attempts to do in any arena of his life, including fighting, to the degree that it surprises him when he fails even a complicated goal, like throwing three darts at a dartboard at once (this took place at a time when he was being followed by a demon that was giving him bad luck).
As a young teen, he decided to take up fencing. He quickly became a world-class fencer and got to the finals in the world championship at the age of 15 (14 in the original story). He then intentionally threw the match because it would be too easy to beat his opponent and he wouldn’t respect himself for doing something so easy.
Here he cuts off a guy's head, but it doesn't fall off until later.
Here he slaughters some Korean martial arts expert mobsters. Note that he breaks a guy's sword and then uses the fork to throw the sword at another guy:
Fighting some zombies, which is so easy to him that he calls it boring and self-indulgent:
He is very accurate:
Even as a child, he could hit a fencing ball without missing, for hours, using either hand:
In one situation, he throws his fork and spears a cigarette that is falling from a window multiple stories above. In another, he spears a cigarette out of a guy's mouth.
Here he uses his fork to deflect a bullet back to the shooter, and even more specifically, he intentionally hits her right in the eye, so it makes a mark similar to the classic Grendel eye:
He intentionally cuts only the fingers off the hand of a guy who's holding a gun on him at point blank range so he drops the gun:
He is very fast and agile:
He likes to jump around the skyline like Daredevil or Batman:
He dodges bullets like any self-respecting top-tier streetleveler. Here he dodges gunfire, then kills the mob's top hitman:
Some more graceful, agile bullet dodging.
Dextrously hanging on a careening car:
Jumping through a skylight and dodging bullets to kill some mobsters (while still unsettled by the demon's bad luck):
And here, in his tour de force, killing 20+ guys before they can barely move. This is pieced together from multiple pages so you may want to zoom in.
This scene is ridiculously good and brings together all his awesomeness at once.
Just as an aside, he's not weak either. Here he holds up a fat guy with one arm. A cop later remarks how much strength it would take to do this:
His weapon of choice:
His weapon, known as the fork, is very dangerous. It is very sharp, capable of cutting through body parts easily.
It can be electrified, and when it is, it can kill someone in one strike. I don’t believe Hunter has ever actually used it to do that, but here is Christine Spar, his successor, killing someone with the same fork.
It can shoot out the fork on a line so it acts as a grapple, or as a way to kill from a distance. It can also shoot the cord out from the butt end to entangle an opponent:
Another scene with the cord:
(It also has a radio.)
I have every appearance of every Grendel, but I am trying to be selective here and not just dump a million pics.
Tomorrow I will go into detail on his fights with his archenemy, Argent, a werewolf with enhanced physicals, and the Grendel/Batman crossover.
Respect Grendel! Vivat Grendel!