Manyu in Vedic sanskrit stands for temper, anger or passion.
The deity Manyu worshipped in this sukta is Lord Narasimha who has victory over anger, temper, etc.
Other devatas such Varuna, Indra and Rudra (Shiva) are also mentioned in this sukta.
[1] Renowned Hindu Saint Madhvacharya quotes Manyu Sukta in the context of Bhima killing Dushasana in the Mahabharata war and said that Bhima invoked Lord Narasimha through this hymn after killing Dushasana.
Vaishnava saint Dhirendra Tirtha wrote a commentary of Manyu Sukta in dedication to Lord Narasimha.