So, here's the thing.
Cyberware/Bioware offers flatly better bonuses to unarmed strikes than any form of magic does.
You're going to want Bone Lacing (Bone Density can offer you the same damage bonuses, but the boosted armor from Bone Lacing makes it far more effective for you) and Striking Calluses (as many as your GM legalizes, 4 is the typical maximum in my experience).
That'll give your unarmed attacks a base damage of Strength+5 Physical.
That's a good start. Begin with Strength as your metatype maximum (10 for a troll) and Agility 4, Reaction 5, and Intuition 4; you'll need those for combat. Get as much Willpower and Body - in that order - as you can with the remainder of your attribute points, to survive getting shot at a lot.
You're now looking at 15P unarmed damage. That's a good stopping point for damage, if you're comfortable with that, though you can get it up to 19P with Muscle Augmentation bioware.
From here, though, you should focus on getting some kind of initiative booster. I'd go for a Rating 2 Synaptic Booster.
After that, the remainder of your attention should be focused on getting as much Muscle Augmentation, Muscle Toner, Platelet Factories, and Pain Editor as you can at chargen, and upgrading the remainder with whatever money you earn during play.
...unless you want to be an Adept. If you do want to be an Adept, take Improved Reflexes instead of Synaptic Booster. Aside from that, though, all of the other 'ware recommendations remain the same. Being a combat punch is very much the sort of thing which lends itself to augmentation rather than magic, unfortunately, with Adepts being more the route of people wielding magical swords.