Im not confused at all at their process. They are in the tier of "we plundered them 4 times, so they should plunder us 4 times max in equal retaliation.
No. The bigger kingdom has the power and means to make a much more substantial strike. The bigger kingdom is also likely making at least 5 times the resources of the smaller kingdom, so 1 plunder for 1 plunder would yield better results for the smaller kingdom. Don't you think being raze killed as retaliation sends a much more clear answer to the smaller kingdom to show them what is accepted and what is not accepted in this game? Maybe raze killing went a bit far, but the bigger kingdom probably didnt have enough provinces in NW range to do much damage outside of razes.
This is a war/strategy game. If you attack a kingdom 5x bigger than you, you have to deal with any and all consequences there are to that. You can't take the moral high ground if you are a smaller kingdom that hits first, and not once, but 4 times, giving relations.
Strato, sometimes the harsh truth is what is needed. Thou shalt not attack thy brother, especially if thine brother is larger than thou, or thy brother shall striketh thee in thine face and make thee pay.