All About Great Knight (FULL Class Guide) - Fire Emblem Warriors: Three Hopes | Warriors Dojo 

My only gripe with the Great Knight is that you can’t make Dedue wear his default outfit while assigned as this class.

Some minor things I didn't mention: Running with this class causes you to knock enemies aside with your shield. This does minor damage. You can activate the unmounted class action with less than 2 shield icons. The area will be smaller.

We need more shield users in musou games, honestly. Something about shields as offensive tools just always tickles me

Actually for some of my axe users I found it more optimal to run them as great knights over wyvern lords, their mounted C3 (the shield bash) does a large amount of damage to shield gages especially when combined with Hildas personal weapon not to mention the follow up with C1 adds a lot of mobility to what would normally be a laggy move. So I build my great knights into shield gage smashers with additional skills that help with damage to shield gages (shoutout to hapi's hidden skill from wyvern knight). Lastly, Balthuses personal skill combos really well with the previously mentioned combo since both attacks activate the "sent flying" requirements to activate it

The reason to play the Great Knight is that it can’t be knocked back while performing strong attacks. Which is really good for units like Dedue and Hilda whose uniques let them charge up their strong attacks but leave them vulnerable.

Yeah great knights are definitely lacking in this game. Since wyvern lords have the grievous blow ability, that puts them above great knights in DPS every time. They're quite good in three houses, cuz you can slap pavise/aegis on them, let them take a bunch of hits on the enemy phase, then put your DPS units to deal damage. But here, the unmounted class action as you said is really the only support ability they have. However, the great knight synergizes well with Dedue and his abilities. His unique is a chargeable strong attack one. His unique support restores the warrior gauge when taking hits while guarding, and restores even more when doing a perfect guard. As a result you end up taking very little damage with Dedue but can dish out plenty of warrior specials. While you'll technically get better DPS with wyvern lord Dedue, it makes a lot of sense that great knight is his canon class.

I'll stick with Edelgard...I'm biases. Thank you for the guide.

It comes at a terrible price. This class has very poor resistance to magic.