Killingham eems below commander level tbh. I doubt Sanji and Franky would be speaking like this of a Cracker or even Jack. They act like Killingham was legit a neg diff
Tbh, Lillingham is a summoner, so it's very believable that he's physically weak
His DF power of dreams materialization is not that combative, it could be more used like a psychological warfare. Now I wonder if Pudding could actually manipulate her DF in a similar manner, with not only editing the memories but also materializing some scary shit from them. After all, DF scope of abilities is very dependent on user's imagination, like Bonney could imagine herself as Nika in the distorted future, which never seemed like her DF power when she was first introduced (she could only temporarily change her own and people's age).