Some goons will invade the Punisher's base, but there is only three of them and they are all extremely weak. The fight will move to the sewers, where more gun battles await with similarly weak foes.
Moving along some of the tougher enemies will appear, including the karate masters and a guy with a flamethrower. As usual many of the basic punks come armed with weapons, so take them out and use their pipes and bats against the other enemies.
You will eventually jump down and find a couple of big gus: Gus and Red, who attack in the same way. There are plenty of barrels around you can throw at them. Going along a little bit, several Pretty Boy robots will drop down and surround you, it can be tricky to get past this part unscathed as they can hit you from a distance. Try just blasting each one with your handgun and keep making them fall back until they blow up.
After defeating the Pretty Boys you will leave the sewer and arrive in a forest. The most basic enemies will once again appear, a few have weapons like baseball bats.
Watch out for barrels in this section -there are a couple of times where three barrels will roll at you, use your special attack to destroy them all in one go and reveal some bonus items. Further along there will be another gun battle, with several handgun and tommy gun using enemies appearing.
Just before the boss you will have to fight a few of the ninjas, who will often use their teleportation powers to get behind you and use their izuna drop move. After beating them, you will move up to a log cabin where the boss awaits: Guard Droid 2.
This is quite a lazy boss as Guard Droid 2 is the same as the first one, but with red coat of paint instead of a green one. So just watch out for his dashing punch, jump kick...
...and laser attacks. Some other enemies will appear as well like Pretty Boys, but as far as the boss goes, use the same tactics for this one as you did with the original Guard Droid.