Having no power to resist; making no opposition.

Incapable of being resisted; irresistible.

impossible to resist; overpowering; "irresistible (or resistless) impulses"; "what happens when an irresistible force meets an immovable object?"

offering no resistance; "resistless hostages"; "No other colony showed such supine, selfish helplessness in allowing her own border citizens to be mercilessly harried"- Theodore Roosevelt