Which is the most dangerous addiction of the following:

TOBACCO

Drugs I dont know how you can say someone is addicted to violence that is illogical. Shows you really dont understand where violence comes from. What you might be referring to is an adrenaline junky and they are actually addicted to the thrill of adrenaline not violence itself. Violence comes from a number of places. Its from frustration, lack of sensation, thrill of danger(adrenaline again). There is no such thing as violence addiction. You simply dont understand what creates violence. I would say drugs since it can end up creative psychotic episodes, violence and reckless behavior, apparently superhuman ability for lack of sensation while high seen in PCP addicts.

Hard drugs such as meth and heroin.

Which ever one kills you first.

There's no black and white answer. It depends on the situation.

The drunk hooker who is on a rampage in the casino trying to score some crack.

Explosives

It's subjective, it all depends on how many people the addiction affects directly and how many people it affects so directly they lose their lives either physically or emotionally.

I will say my guess would be violence. If someone goes out day after day with violence as their focus it wouldnt be an awful long time till he or she had focus on someone else that wasnt taking shit from anyone and pretty much took out the violence junky with gun or knife. Now on another note the past 35 years off and on I have used recreational stuff, it had many chances to take me out, but Im still here. That makes me think God has a very focused intentions for me at my time.
I know, I have stupid tattooed across my face, right ?

Internet/technology.

I would say anything that is able to not only kill the person taking it but allow that person to kill others as well. It also depends on the person using it.
I would say in my opinion gambling is the least dangerous. Everything else except other that you listed could end up killing themselves or someone else.. so yea.