Here is another commentary which re-affirms my opinion..
http://chareidi.shemayisrael.com/archives5766/kisiso/oraltskykss66.htmOpinion & Comment
After Your Enemy Falls . . .
An adaptation of the sichos of HaRav Chaim Dov Altusky, Shlita
In Pirkei Ovos (4:19), Shmuel Hakoton quotes the posuk, "When your enemy falls, do not be happy. And when he falters, your heart should not be filled with happiness: for the Ribono Shel Olom may look into your heart and see how happy you are over the fall of your enemy. And He will not like what He sees in your heart. And then Hashem will withdraw His anger from your enemy" (Mishlei 24:17,18).
With a surprising chiddush, Rashi explains that not only will Hashem take away His anger from the enemy but also, the enemy will be forgiven of all his sins. Remarkably, the Ribono Shel Olom reverses the verdict of someone who rightfully deserves punishment simply because people are happy over his demise. Furthermore, those who are happy over their enemy's downfall will incur the wrath of Hashem.
In his commentary on Pirkei Ovos, Rabbeinu Yonah adds an even bigger chiddush: This process occurs even when the enemy is a rosho, meaning that Hashem considers him a rosho because he is predominantly a baal aveiroh! He has very few mitzvos to counterbalance those aveiros and therefore receives his punishment.
Nonetheless, Shmuel Hakoton teaches us not to be elated over his suffering. Since, as Rabbeinu Yonah puts it, "A person should only be happy because of the kiddush Sheim Shomayim that is occurring for the benefit of the Name of Hashem Yisborach."
When a rosho suffers because of all the pain he has caused, this sanctifies the Name of the Ribono Shel Olom. Therefore, we should be happy because the rosho receives his due punishment. When people witness a rosho running rampant by treading upon the feelings, sensitivities, and lives of others, the rosho feels— and his victims believe—that he is master of his and their destiny. Then, when his punishment comes and he falls, this sanctifies Hashem's Name.
Therefore, it is very good if we are happy because of the kiddush Sheim Shomayim. Nevertheless, Rabbeinu Yonah warns us: Even a tzaddik should not experience personal happiness over the fall of the reshoim. Through the demise of reshoim, people see how Hashem has revealed His complete control over all events. Therefore, the focus of our joy is kvod Shomayim. We are happy because the world realizes that the Ribono Shel Olom is always in control. Hashem has brought about the enemy's demise.
We must not harbor a personal hatred for the rosho nor seek personal revenge. This is so even if this rosho has caused us great personal aggravation and suffering. Even if we have many good reasons to pray and seek his downfall, nevertheless if we will be happy because we hate him for what he did to us, to our families, and to others, then Rabbeinu Yonah says, "The Ribono Shel Olom will cleanse and forgive all this rosho's aveiros."
I will agree that it seems that the Rasho which is referred to is a personal enemy and not a national enemy...