Fire Emblem Awakening [SPOILERS INSIDE]

The trick is to distract him and have his AI attack someone from a distance who cant retaliate. It's just hard because a lot of those people who are able get screwed by sages.

It helps to pair up people who have Galeforce. Having the ability to move 3 times in one turn helped me take out all of the sages and snipers around him, so they wouldn't gang up on Chrom when I moved him near him.