Kled will work great with Champions that either need some sort of way into the back line or have a way to lock up the enemy team for your ult to catch up, so examples are Amumu, Darius, Garen, Any assassin(Fizz, Zed, Kata, ECT.), Sejuani, Galio. Other Champions that will work well with him are champions like Janna, Sivir and Tahm Kench. Most of the time you will want to be the one starting team fights with your ult and letting your team follow, But in some cases it is better to start with a AOE crowd control effect so that you can help your team catch up to the fight, for example you as Kled, your adc and support are at Dragon just finishing and your jungler, who we will say is Amumu, and mid are in a bad spot, if the Amumu were to ult it would buy you and your bot lane enough time to catch up(assuming they are not top lane) and turn the tides of that team fight. Kled is a champion that Heavily relies on his team otherwise he will be just another tank diving in with no backup, for this reason it is better to draft the champions on his team around him or pick him if you see you have a good team.