The Holy Spirit specifically is said to grieve because He is the unifying presence dwelling within believers — our division grieves Him most directly

The Father and Son also grieve (Jesus wept, Jesus grieved over Jerusalem). But Ephesians 4:30 focuses on the Spirit because of the specific sins in context — bitterness, wrath, anger, clamor, slander, malice (Eph. 4:31). The Holy Spirit indwells believers and is the unifying force in the church. When believers cause division through these sins, they grieve the Spirit most directly because He is the one within them whose work is unity. The seal of the Spirit ("by whom you were sealed for the day of redemption") makes Him the most intimately affected.