Complex sentence: When the real Atlee arrives, Hunt forces him to admit that he began the Syndicate without permission, and that he has been covering up its existence after Lane hijacked the project and went rogue, turning the Syndicate against him and MI6.
Split into simpler sentences: When the real Atlee arrives, Hunt forces him to admit that he began the Syndicate without permission. Atlee admits he has been covering up its existence after Lane hijacked the project and went rogue, turning the Syndicate against him and MI6.