listen i haven't finishe demon slayer yet, but i do know that tanjiro is not at his full strength yet in that photo and i'm not too sure about the other photos so im not too sure who is strongest
I have finished all of them (atleast to the latest chapter) so I can asure Tanjiro is going to be way more stronger but all of the other 3 are also strong so i also don't know what to say here