In the story I'm currently working on an alien race holds the monopoly on FTL travel. They're using a modified Alcubierre drive system, powered by Negative Mass. Humanity stumbles on a source of Negative Mass, and with assistance manages to bootstrap an FTL drive for themselves.
The aliens have always jealously guarded their monopoly (picture a society based on similar lines to the British East India Company), so inevitably there will be a battle. The aliens have traditionally relied on their speed to take them out of harms way, as they're merchants at heart rather than warriors. They have always relied on Economic warfare, as opposed to combat, though when the need arises they have no problem hiring mercenaries to do their dirty work.
At the end of the tale we have a human FTL ship chasing down the alien vessels. My question is this...exactly how would they do that? What kind of weapons and tactics actually work at FTL speeds? Lasers and other energy weapons are limited to light speed, and the Alcubierre drive is too massive for missiles. Not only that, their supply of Negative Mass is limited, so what are their options? Outside of ramming the other ship, that is, I'd like to avoid a kamikaze approach. Boarding actions are possible, but a suboptimal choice.