Jesus had to come and die because sin has to be punished and God is a just God. so on the cross the wrath of God, the hatred of God towards sin, the love of God for us, all of this is shown on the cross. the question of suffering is a challenging one for all and as far as i am aware the christian approach for this question is that we are living on a fallen and soon to be destroyed world. so all kind of evil,bad doings, unfairness and sufferings are expected. it is painful but imminent. But all will end one day. and as the one scholar pointed out "Justice delayed is not necessarily justice denied. There will come a day when God will settle accounts and people will be held responsible for the evil they've perpetrated and the suffering they've caused. Criticizing God for not doing it right now is like reading half a novel and criticizing the author for not resolving the plot."