The DM who is confrontational and sees the game as 'Me against them'. I have played with killer DM's. One of my first DM's was like this. We would go through several characters a day sometimes. When He got bored or the players started to get 'too powerful', TPK time. Later, when I experienced a good DM, I couldn't believe all that we had endured and continued playing despite of it.
The DM who believes 'It is all about Me'. I have played with the cheater DM. The one who rolls just for the sound of it, but knows if it will succeed or fail before the die hits the table. They tend to have a story or world that is more important than the players. The last would rule zero every time he was caught bending the rules past breaking. One of the last games I joined was like this. The DM was only concerned with his fun, and changed rules on whims only to change them again later when it best suited his desires.
The power trip DM who believes 'Everything is Me'. I have even experienced this type of DM for short periods. One was a bad Warhammer player who decided he could DM a D&D game. He could never get out of the wargame and was just too thrilled to be in the driver seat. Anything went depending on his moods and when he decided to 'win'.
When I DM, I try to never make the 'run away or die encounters'. On the rare occasion I cheat, it is in the players favor because things are going bad despite their best effort.