Try out a tanky AP champ or a tanky build and you should have some better results. Viktor with RoA, Liandry's, Rylai's, Rabadons, Sorc Shoes, and Death augment. You poke them with your laser from outside of their range then when they engage you simply blow your combo with your ult to stop their combo while you grape them.
I played Viktor mid against a Pantheon the other day, laser poked him down. When he jumped on me I came out ahead due to being ready for his combo. Late game I had like 3k health and would never die in teamfights.
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