Would it be wrong to want my kind and supportive friend to suffer?
Why would you want a good friend to suffer?
I feel like he could be happier if he suffered.
Even if you feel that he may improve as a person from suffering, it is not nice to wish ill on anyone. Wishing ill on someone who has done good to you seems even worse than wishing ill on a random person.
I don't care. I see through his niceness and think he might be the worst person ever.
He is your friend who is kind and supportive towards you, so why not return the favor and be kind and supportive back? Wishing bad things towards people is bad, and people won't like that you're doing that-- they might even decide to dislike you over it.