The Assassin's 'Death Attack' isn't going to be very good unless you are going to take some levels in the class...
the victon gets to make a Fort save vs DC10 + assassin's class level + Int bonus.
Another option would be the Shadowdancer. When you and your Shadow companion attack someone, you would automatically get the flanking attack bonuses (sneak attack) And the Shadow is going to be STR damage every round (if he hits). It doesn't matter how many hitpoints your target has if the Shadow is doing STR damage...
the victon gets to make a Fort save vs DC10 + assassin's class level + Int bonus.
Another option would be the Shadowdancer. When you and your Shadow companion attack someone, you would automatically get the flanking attack bonuses (sneak attack) And the Shadow is going to be STR damage every round (if he hits). It doesn't matter how many hitpoints your target has if the Shadow is doing STR damage...