Despite being the primary victim Saren is a victim of the Reapers. Unable to see pass his indoctrination there’s 1 way to get him to see the truth. It’s too late but Saren can redeem himself in his final moments and save you 1 boss fight.
The first part is during the raid on his facility. Regardless of who you choose to save Saren will appear. During the final set of choices, if you have enough Paragon or Intimate points you can choose to plant the seeds of doubt.
Once done you’ll face Saren in the Citadel and he’ll mention how you got through to him. But he then allowed Sovereign to implant him with Reaper technology. Choose “You’re Indoctrinated” to option up the Paragon and Renegade choices. If you have enough you can trigger Saren attempting to fight back. The last set is only available if you maxed out either side, allowing Saren to take control of a brief moment and end himself.