You can take down Agent Smith without a wall kick, even if temporarily. First, scoot back so he does not throw you, then equip any gun and fire. At the same time, go into Focus and, while he is evading the bullets you just fired, run in then punch or kick him until he goes down. Kicks are recommended because they are more powerful. After that, get out of there while still using Focus. When you are out of harms way, let off the Focus. Note: Doing this in cramped spaces such as hallways is not recommended unless absolutely necessary.
When facing the Agent Smiths, there will be a level where you find a grenade launcher. Stay far back when shooting or you will hurt yourself in the explosion. The Smiths will die with about three shots from the grenade launcher. Be careful -- even when you have infionite health, you could be blown off the buildings and die. Also, do not get close to the Smiths or they will throw you. When a Smith dies, you can pick up an actual Agent's gun (the .50AE), which can be used in dual handguns. These handguns are the most powerful in the game.
With a 40 mm grenade launcher, go into Focus mode and shoot him three or four times. Look again and he will be dead on the floor. You can take his gun if desired. Kill another one to have a double weapons.
In one of the Chinatown levels where you escape from Agent Smith, there is a grenade launcher somewhere. Three shots with this will kill Agent Smith.