Who to give Close Counter to....

Close clounter is pretty hard to use for ranged units because of their lower BST, but the general rule of thumb is to use it on mages with high defense and good attack.

Henry, Leo, Boey, Spring Camilla, and Armored Lyn are some good options.

Lachesis with Absorb+ seems to be another option floating around for Close Counter.

Gordin, Leon, and NY!Corrin are also options, although NY!Corrin has limited merges.

I'd add Sophia to the lists already given, she can have decent mixed defenses and who knows, might get a weapon upgrade eventually. Also plenty of merge potential.

Moving to daggers Saizo has the defense to pull it off and I've seen some nice Felicia builds that combine it with Vantage.

Whatever option you take, I wouldn't recommend using it on Dr.Sakura with Def bane.

if youre gonna make sakura into a cc healer id recommend not -def. literally anything else.

My jaffar has CC and vantage, saizo can work too with his high def stat.