Obstruct : block (an opening, path, road, etc.); be or get in the way of. Challenge : a call to someone to participate in a competitive situation or fight to decide who is superior in terms of ability or strength. Damage : physical harm that impairs the value, usefulness, or normal function of something. Ruin : the physical destruction or disintegration of something or the state of disintegrating or being destroyed. Hinder : make it difficult for (someone) to do something or for (something) to happen.