What FE chapter made you suffer the longest?
Personally, it was the chapter when they introduced the ballista in FE7. I dont know why I was stuck on it though...
OH WAIT I KNOW WHY!!! ITS BECAUSE THE BALLISTA IS BULLLLLSSSSSHHHIIIITTTTTTTTT!!!!!!
but seriously...the ballista is annoying af.
It took me to my wit's end but after 1 hour of pure torture I realized that I just have to wait for the enemies to rush me than I can just demolish them...I was able to kill the Ballista Douche shortly after.