sigh yet another person who simply didn't know how to build to counter targon. He's durable yes, but his damage is not actually that high. He has a lot of CC, but his ability to burst anyone is among the lowest in the game due to very poor scaling AD ratios. That said, with burning armor and tank stats, he can kill snipers decently well if yo udont' know what you are doing.
3 ways to counter him.
1) Dodge his Axes. Their dmg is only impressive at rank 1 and low levels. Doing this denies his only way to poke, and his only way to force early engages.
2) Carry Bonus - the 50% healing reduction shreds his ult healing. As well, since he often builds health, this will scale well to shredding his hit points.
3) Kite commanders - Nefara and Eos both hard counter targon as a team comp. Both of these commanders are very good at kiting, and Nefara also is even better are zoning and suppressing him.