It was posted in another thread, it was available to all. There is no unfair or inherent advantage to anyone.
The bonus is exactly what the value is of a whole team. If a team is worth 33 points, finishing off the opponent will net you another 33 points so 66 in total. What to take from this is to make sure that you finish off an opponent as it is necessary to score the most points.
If you kill 4 members of the team that would normally net you 33 points, you will get somewhere around 27 points for that. If you take out the remaining hero, you will score 6 points for that hero and then another 33 points for the finishing kill bonus. Whether you were able to accomplish this in one hit or in 5 hits, the total net gain is the same. The 66 points would be available in total to all, whoever does get the finishing kill will be the only one that nets the bonus points.
Let’s say there’s a victory bonus of 20% of the team’s HP value. So a given team may have 25 points from HP, plus 5 points for the victory bonus. I take down four of the heroes with my first run, scoring 20 points. I go in again, kill the final hero, scoring 5+5 = 10.
@haylc is right; on beta and first war it was 100% bonus for finishing off an opponent.
I’m a little concerned that alliances are going to run out of flags with the new respawn timer. Guess we’ll see how it goes, but last war when I got on late (6h remaining) there were very limited targets and it’s going to be worse this time without the revive bug coming into play.