This is my ranking after fully upgraded. This isnt considering price.
?=havent used
HM=honorable mention
Inf
1. (Tied) -Marshall: Has infinite health when used properly, deal 700+ damage when around other inf gens
-Simo Hayha (debatably): So much damage, infantry killer when paired with hawkeye force
3. Yamashita: no explanation needed, best non iap inf gen
HM: Runstedt
Tank
1.Wittman (imo): hes my main tank gen and can easily deal high damage, lacks rumor tho
2.Manstein: No explanation needed. 6* Mob, best tank skills, just add rumor and inspiration and hes deadly
3.Tolbukhin?: Can deal extra damage with tanks around him, best skills, again no rumor, 5* Mob tho
HM: Guderian, List, Abrams?
Art
1. Kluge: Highest damaging gen (behins marshall with units arouns), i use him with the excellency medal, deals 2000-3000 dmg per turn
2. Zhukov: Add rumor, deadly
3. Konev: same with zhukov, but a bit worse
HM: eichelberger, Leeb
Nav
1. Raeder: imo better than donitz and nimitz when maxed out
2. Donitz: best sub gen
3. Nimitz: cheap with discounts
HM: Yamaguchi?, nagumo, mikawa
Carrier Air
1. Spruance: At 1st i had doubts, but the +50% damage really hits hard
2. Yamamoto: best non-iap carrier gen
3. Other 6* Air Gens
Air
1. Colson, cracked at conquests
2. Spaatz, no anti air? Thats a yes for me
HM: mccampbell?, the german gen(i forgot his name)?, Arnold, Chennault.