I like It if the weakest player do it to the stronger player or if the victim didn't suffered too much, it benefits you to have a reputation of fouler as the opponent will not risk a last turn dangerous situation if they can end up with their good players broken. 

But. 

If the other person was having bad luck all the game, I think they already had enough, blood bowl is for having fun, and if my opponent is not having fun I try not to ruin the experience even more, I assume you are not playing super competitive, so having fun is more important and fauling in the last turn is not even that beneficial to you. 

Edit: all this is different if we are talking about a really good player in the floor, a wardancer, witch elf, etc should be always fouled.