The Greek word translated as "complainer" means literally "one who is discontented with his lot in life." Complaining is undoubtedly not a fruit of the Spirit (Galatians 5:22-23) and is detrimental to the peace, joy, and patience that come from the Spirit. For the Christian, complaining is destructive and debilitating personally and only serves to make our witness to the world more difficult.
"But the fruit of the Spirit is love, joy, peace, longsuffering, gentleness, goodness, faith, 23 Meekness, temperance: against such there is no law" (Galatians 5:22-23).
Amen!