Dmitri will die when he fights Shinji and AsukaHe is a loose canon and a violent, blood-thirsty psychopath is probably beyond recovery and salvation and is a danger to everyone. And nobody likes, In-Universe or in Real Life. If he survives, he will be a constant threat to the main cast. So he will do not.
The mysterious person gave Ritsuko intelligence about SEELE and hired Dmitri is YuiIt would explain why that person shed a tear while watching a video of Shinji hospitalized, why that person intends to destroy the remnants of SEELE and why Dmitri asked if he or she was looking for everyone's forgivenness. Maybe Kyoko is helping her.