Defeat Jimmy “Deathtrap” Oneill
This cave is located northwest of Mataka Village. The cave is also known as Tuluga Cave. There's a lot of walkers and infected inside, including the boss zombie, Jimmy. It will help bringing a friend to help you out but it is plausible to do it alone, as long as your level is fairly high with some fairly powerful weapons.
Defeat James “Killer” Nisira
If you enter the bungalow, you'll be able to start this sidequest. Make sure you have powerful weapons and explosives with you, as well as a good number of medkits. If you're having difficulties, have someone play with you.
Kill Olivier “Deathbone” Wenge
This boss zombie is found inside Olivier Wenge's Hideout in the middle-northern part of the island. There's a lot of walkers and infected inside, including the boss zombie, Olivier. It will help bringing a friend to help you out but it is plausible to do it alone, as long as your level is fairly high with some fairly powerful weapons.
Kill Peter “The Undying” W. Spicer
This deadzone contains frenzied infected, which are more dangerous up close. If possible, use ranged attacks or thrown weapons to stop them on their tracks. Thankfully, the boss itself is a thug-class zombie so you can easily lay down mines and throw grenades at it.
Defeat Eduardo “Quickdeath Petoia”
This is the boss zombie inside the Ocean View Bungalows deadzone and will drop the antidote needed for the sidequest of the same title.
Defeat Joe “Ogre” Somare
When you're saving Marcus during the mission "Saving Holy Man", this is one of the zombies you have clear in the area where Marcus is.
Defeat Frankie “The Scourge” O'Hara
This boss zombie is a grenadier found in the deadzone basement north of the cinema. There's a lot of walkers and a screamer along with him in the bottom floor so it will be a good idea to take cover and lob explosives inside. Avoid facing him face-to-face since the water will severely affect your movements.
Defeat Metzger “Skullcrusher” Sloat
This boss zombie is found in the deadzone basement south of the cinema. Aside from a good number of walkers, he is also accompanied by a screamer. Lobbing grenades as soon as you open the door is a good way in clearing the room. He's tough and may even force you to go upstairs. If you have modded firearms, aim for his head since his really slow movement will be his weakness.
Defeat George “Flesh Eater” Serero
This is a thug-class boss zombie inside an aparment in the southwest portion of the city. The area is filled with several walkers so this should be easy enough to clear. There's a Striker Rifle Mod blueprint the second floor so don't forget to clear it as well.
Defeat Doctor “Scar” JJ Evans
This is a thug-class boss zombie inside his own clinic southwest corner of Villa Henderson. He is accompanied by walkers and a few infected so it should be easy enough to clear it.
Defeat Geoffrey “Walking Carcass” Nape
This boss may be registered in your casebook since he will appear as a boss in the military base. However, you need to enter his warehouse located in the middle-west part of Henderson, a few steps south of the passage leading to the military base, and defeat him there. You'll also find the blueprint merchant NPC (Alex) outside the warehouse who you can rescue.
Defeat “Blackheart” Chubalba
This is a frenzied infected-class boss zombie found inside his own motel in southwestern Henderson. He's the greatest threat in the area since he's accompanied by walkers only and a handful of infected.
Defeat Ogio “Blindspot” Moke
This is a frenzied infected-class boss zombie found inside his own laundy shop in the southeast portion of the town.
These zombies are incredibly powerful, deadly, has no weaknesses and even regenerate their health for every successful attack. They are holed up in their own deadzones and the only way to win against them is sheer firepower and strategy. You have to defeat 13 boss zombies to unlock the achievement "Hunter-Seeker"