The best assassins don't leave a mark. Weapons, poisons ... meh. Any old idiot can do a drive-by.
All any Patron needs do is just tell some hardcore grunts in a local bar that XYZ, his target, secretly likes children way too much, and get them to corner him in a parking lot one night with bricks.
But knowing the guy's habits and patterns; exploiting his weaknesses; sabotaging the target's technology - there's the art.
So they have a signature gun with biometric pattern recognition, keyed only to them. Cool. Go into the gun's computer and scramble the data, locking it out from everybody. The first battle they go into, their gun jams - game over.
So they have a grav belt, and can fly about. That guidance system needs a quick update. One which will immediately shoot them straight up into orbit without a vacc suit the moment they hit 100 kph. Bye bye birdy.
Moi, I'd find it hard to play any kind of an assassin. The faces of the victims would haunt me. Not the character. Me.
Your mileage may vary; but this bit is important. It isn't advanced tech and weaponry, or poisons, that makes the assassin. It's patience and perception, and gaining the measure of the target through detailed covert surveillance and intel gathering.
The best assassins work up a detailed dossier of the target's habits, and work out the weak spots where, with a little tweaking, the hammer can fall down in such a way that it looks like a freak accident.
Nobody would question someone getting run over in the street, even if they did swear blind that the lights were green (and you'd have sabotaged the readouts so that, just this one time, they were green while the lights still read as red). Nobody would question how the married victim came down with a debilitating social disease; they'd only notice the fact that he got it during an assignation with his mistress (a sneaky swab on the victim's plate in the kitchens of the restaurant? No problem).
Lastly, if your assassin has conducted more than one murder attempt, that means he is likely to be a survivor of any number of attempts made on his own life by the people he'd been hired by.
First rule of assassination: kill the assassin after the hit.
