Oroku Saki, also known as the Shredder is the main antagonist of the 2018 Rise of the Teenage Mutant Ninja Turtles series, serving as the overarching antagonist of the first season and the main antagonist of the second and final season. He is the true leader of the Foot Clan as well as the archenemy of Splinter and The Turtles.
What makes him Pure Evil:
Despite of all incarnations of the Shredder is Oroku Saki, this version of the Shredder is very separate to Oroku Saki meaning Shredder is the Dark Armor called "Kuroi Yuroi" and Oroku Saki is just a heroic protector who mistakenly made a deal with the Kraang
As the armor he swallows Oroku both body and soul becoming into the terrible demonic warrior himself
Using Oroku Saki's authority, the Shredder lead the Foot Clan down a path of villainy, destroying many innocent lives in the process
500 hundred years later he possesses Draxum so he can be defeated which thjis is how he becomes free
While the fact after he's free, he currently turned like a mindless monster he makes servel massive damges in New York City
After Splinter, Draxum, and the Mad Dogs managed to obtain the information involving the required means to defeat the Shredder through Splinter's memories, they went to the Twilight Realm to retrieve the weapon mentioned. The removal of the weapon, which was revealed to be Karai herself, released the Shredder's sentient spirit that was sealed in the realm which returned to his empty vessel, allowing him to speak and overcome the collar's control with his full power finally restored.
The Shredder, desiring both revenge on Karai for defeating him in the past and invincibility by stealing her essence, left the Foot Shack to immediately besiege the lair where she was located
He successfully kills Karai and destroy the Turtles mystic weapons
Kidnaps Splinter so he can take all his power for more power
He doesn't care about his minions so he just abandons them behind while stuck in the rocks
He ordered Casey to create the ritual that would drain the essence from Splinter while he accessed the Empyrean
While the fact Oroku Saki redeems himself after the Shredder armor is destroyed, the Shredder armor itself still did ultimately evil deeds even despite itself is just an dark evil armor
Conclusion: Just in my opinion, yes