The Battle of Flodden was in 1513 was devastating to the Scots.  This was the largest battle ever to be fought between Scotland and England.  Along with the death of King James IV were the deaths of nine earls, fourteen Lords of Parliament and several Highland chiefs. James' son, Alexander, the Archbishop of St. Andrews, had also been killed, along with other prominent churchmen. In all some 10,000 men, a third or more of the Scottish army, had been killed. 

Further details can be found on this link.