1) Atbay 2) Engulfed 3) Helpless 4) Impotent 5) Incapacitated 6) Ineffective 7) Ineffectual 8) Inundated 9) Overcome 10) Overpowered 11) Overwhelmed 12) Unable 13) Uneffective 14) Weak 15) Weakened 1) Dead in the water 2) Dependent 3) Engulfed 4) Feeble 5) Flooded 6) Having no clout 7) Helpless 8) Impotent 9) Incapable 10) Incapacitated 11) Ineffective 12) Ineffectual 13) Inundated 14) Lacking power 15) Low-powered 16) Marvel Comic title 17) Overcome 18) Overpowered 19) Overwhelmed 20) Rock ballad 
• (a.) Destitute of power, force, or energy; weak; impotent; not able to produce any effect.
Pow'er·less adjective Destitute of power, force, or energy; weak; impotent; not able to produce any effect. -- 
[adj] - lacking power
adjective lacking power