I would have to say the worst character I have ever seen was one of mine, after I had been gaming for years. It was not for a bad build, it was a Rogue, optimized for finding and disabling traps, and he set off every trap the party encountered. Not because I didn't search, but because I failed every check to find them, and then walked right into them. I didn't get it, I did not build him for combat, but got more crits than the Fighter of the group, and even healed the Cleric when he fell in battle. Ultimately, he died to a trap.