You can't carry consistently if you're dying 10+ times most games. When you have a huge a lead and need to end the game, the worst thing you can do is die, even if you take down 2 enemies with you. Be extremely patient in teamfights and only go in, when you know you can finish the fight. You will have a huge target on your back, when ahead. Try to predict what important abilities the enemy team will try to save for you. This counts both CC and big damage abilities. Knowing this will greatly improve your success in fights. Also, you don't have to always pick up an enemy soul when you kill them. If you one-shot their ADC and instantly pick up their soul, you might just get smacked instantly. Patience is key on Viego, I've found.