It wouldn't be a Metal Gear game with out some bizarre bosses. Below is a list of bosses that you will have to fight and kill in order to advance further into the game.
Chaigidiel is among the more recent experimental subjects. His main fighting technique is to manipulate his enemies as well as his allies with hypnotism. He can also handle various weapons with great skill.
Golab is another experiment performed by SaintLogic Inc. He can spew scorching flames from his skin using the large amounts of oils stored in his body. To stop him from receiving burn damage, his skin regenerates quicker then an average mans.
 Harab Serap
This creature towers over two metres tall and is another former experimental subject of SaintLogic Inc. He attacks by lunching detaching arms at you and then later regenerates them afterwards. He can alter the shape of his arms depending on the situation. Serap can also reduce damage from explosive impacts with his tough durable skin.
Vince comes from an extensive military background, and works with a high degree of professionalism. No matter who employs him, he will place all of his energy into his work in order to get his pay at the end of the day. His former colleagues from the military followed him when he started working as the Director of Security at SaintLogic.