If "avenue" means a street or road:
* Byway: A less traveled road, often rural
* Lane: A narrow road
* Path: A narrow, unpaved road or trail
* Dead end: A road that ends abruptly
* Cul-de-sac: A street with a circular end
* Back alley: A narrow, secluded street, often associated with undesirable activities
If "avenue" means a way or means of achieving something:
* Obstacle: Something that blocks progress
* Barrier: Something that prevents access or movement
* Blockade: An obstruction that completely prevents passage
* Impasse: A situation with no way forward
* Dead end: A situation with no solution
If "avenue" means a wide, tree-lined street:
* Narrow street: A street that is not wide
* Unpaved road: A road without a surface
* Rural road: A road in a countryside setting
The best antonym will depend on the specific context in which you are using the word "avenue".