6. LOUIS XV
If you are going to attempt to kill a member of a royal family, especially a king or queen, then it is essential that you ensure to plan your attack thoroughly. After all, you are only likely to have one opportunity to do the deed and a small window of time to carry out your plan. Someone obviously did not give that advice to Robert-François Damiens, who made an incredibly poor attempt to assassinate Louis XV of France.
Having managed to slip passed the royal guards protecting the king, Damiens was able to get close enough to Louis XV so that he could stab him. Fortunately for the monarch, the would-be-assassin had only thought to bring a small pen-knife blade. The small blade size and the fact that the king was wearing multiple layers to keep him warm during the winter meant that the wound was less than half an inch thick. Guards quickly sized Damiens and he was executed two months later.