This, in my game anyways, is the equivalent of a death sentence. Just merely uttering the phrase is enough to make any player, not just Jedi, stop and seriously consider what they are about to do.
The reason for this is not just the implications of gaining more than one dark side point. The way I use dark side points is, if character gains one, they cant gain or use their character points without atoning for the DSP. So effectively, the only way they can continue to be powerful is to either get more Dark Side Points or seriously atone for their indiscretion.

However, tempting player characters is rather difficult to do I have come to realize. The players know you are tempting them and it is difficult to get them to play their characters without this knowledge. Therefore, I try to use other devious ways to lure them to the darkside.
One of my favorite, albeit overt, methods is to offer them extra dice to take the easy path. Most times in a desperate situation where the outcome looks bleak and it would be easy for the Jedi to just squash the enemy I will offer extra dice black in color and suggest the Jedi "try doing THIS..." Most times they decline the dice and figure something else out; but they do hesitate and consider it.,which is what i want them to do.
I like to play up the internal struggle and I also create a lot of morally ambiguous situations. I'll throw a heartless serial killer at them, then ask the Jedi if it is okay for them to just slaughter the guy because they caught him.

Using moral roleplaying is just as effective sometimes. It works for me, and my players seem to enjoy it.