Re: a suspenseful fight sequence between....
In film (I suppose in literature, but I associate it with film) a sequence is series of actions. You can have a car chase sequence or a fight sequence, for example. In the latter, there is a fight.
In this fight, it was between the two characters as described above. Watching them fight was supsenseful (made them feel anxious, for lack of a better synonum) for the audience.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.