It is a dark night and an innocent civilian is floating along a alleyway when someone jumps them. They have a bat and want the civilian's money. But if the mugger hits the person they will fly away and might escape. The victim is wearing a jumpsuit with zippered pockets and the money is in their pockets. How can I mug someone properly in 0 g?
Not a bat!
Not even a knife
In a zero-g environment, it would not make sense to use a swinging weight to attack. The inertia will cause you to counterrotate, and yes if you do land a hit you will tend to shove your target away.
You would either grapple, thus enforcing contact and preventing escape, preventing loss of target, but exposing yourself to counter-grapple.
Or, you would use a non-inertial means to disable your opponent.
How about a nice tazer? Or an aerosol spray with a knockout gas? You could protect yourself with a mask or even just a nose filter. Additional plus, having a canister with a trigger on it in your pocket is not very suspicious, but moving around with a blade or a great big Bat would draw attention your mugger might not want.
P.S. Do you have to mug? Pickpocketing should be much easier in zero-g, as the lost weight of a missing wallet/device/card will not be obvious at all. And it is SO easy to blame an "accidental" collision on the natural clumsiness of a biped without ground under its feet.
The obvious answer here is that the mugger fixes the victim to keep them close. Either they grab them with their hands, or better have a device that locks on and grips the victim without harming them, and can be released by the attacker. This allows the assailant both hands free to actually fight if needed.
Being that close makes a bat an unlikely weapon. A knife would be much more useful. And this approach makes the mugger much more vulnerable to a sudden attack by the victim with a concealed weapon, or even superior close fighting skills. Superior numbers would be an advantage, possibly with one of the attackers not locking on at first.
A better approach is to use a small crossbow or harpoon-like weapon, which would not impart much momentum to either shooter or victim, but would do substantial damage. A harpoon would prevent the victim from drifting away. Combining one mugger who attaches themselves to the victim, and another who has a harpoon would be hard to counter.
Just tether them out of reach of any graspable surface- and they are stranded without propulsion unit. All that is needed is some "smart" rope keeping them centered.If there is no other force - no collision and you have nothing to sacrifice (like a purse) - you will be stranded in mid-room, tunnel, hoping for a breath of air to drift you to a side-rung.
Same physics shenanigans apply if you accelerate. There is no gravity to break your flight. Accelerate somebody, and without a tool to physical brake - they will shoot along the tunnel, till they come out the other side. Want them disorientated? Spin them. Im not responsible, for the crime rate of the ISS.