Vader probably carried a death wish to a certain degree which would have made many of his actions insanely bold.
After the death of Padmé, he lost his limbs were removed in the fight with Obi-Wan and his body burned as a resultsuffered severe bodily burns. Once in the infamous suit, it restricted his ability to utilize the force to its potential (eg. use of Sith lightning), and also restricted his agility.
The book Dark Lord, by James Luceno, saw Vader go on a hate-fuelled rampage, full of bitterness, in the knowledge that he would probably remain the lapdog of Sidious forever.
If anyone had a reason for a death wish, Vader had plenty.