Any structure that makes progress difficult
Impediment
Impedimenta
Obstruction
Obstructor
Construction
Structure
Block
Blockade
Blockage
Closure
Tumbler
Barrier
Preventative
Preventive
Stop
Stoppage
Bar
Encumbrance
Hinderance
Hindrance
Hitch
Incumbrance
Interference
Obstacle
Occlusion
Obstruct
Someone who systematically obstructs some action that others want to take
Obstructionist
Resister
Thwarter
Disputant
Eristic
Controversialist
Naysayer
Stonewaller