What do we learn from "Al Tischar ba'Mre'im"?
Megilah 6b: If a Rasha is enjoying good fortune, do not confront him.
Rashi: Do not try to be like them, like "v'Eich Tischareh", "Ki Atah Mischareh ba'Arez" (Yirmeyah 12:5, 22:15).
Malbim: One who sees Resha'im succeed, either (a) their deeds are bad in his eyes, and he does not envy them to be like them, but he is angry over their success and complains that Hashem does not punish them. "Al Tischar" - do not be angered over their success. (b) Refer to 24:19:3:2.
Our verse forbids confronting Resha'im in this world. "Ozvei Sorah Yehalelu Rasha v'Shomrei Sorah Yisgaru Vam" (28:4) implies that one may!
Brachos 7b #1: Our verse means, do not compete with or be envious of their deeds -- "Al Yekanei Libecha ba'Chata'im Ki Im b'Yir'as Hashem Kol ha'Yom" (23:17).
Brachos 7b #2: Do not confront a Rasha in his affairs, but confront him in Heavenly matters.
Brachos 7b #3: Both of these discuss Heavenly matters - do not confront him when he prospers.
Brachos 7b #4: Both of these discuss Heavenly matters - a total Tzadik may confront a Rasha; a Tzadik with some sins should not.
Why does it say "Al Yekanei ba'Resha'im"?
R. Yonah: In many places, this Sefer warns not to envy Resha'im - "Al Yekanei b'Anshei Ra'ah", "Beni Al Yekanei Libecha ba'Chata'im" (1, 23:17). It need not warn not to envy their sins, to do evil like them, rather, not to envy their serenity, wealth and honor. It does not warn against desiring wealth and honor. Often one envies wealth and honor, for he sees that others have it, and he thinks that if he had it, he would acquire an attribute. The verse commands not to envy their evil - one should despise and disgrace it 1 . Even if they have wealth and honor, we know that their end is to be finished and utterly destroyed. Their wealth and honor are no advantage for them.
Malbim: One who sees Resha'im succeed, he might envy them to be like them. "Al Yekanei" forbids this.
R. Yonah: If one sees wealth and honor as a leper and a pained Choleh, he would not envy it. He will not be glorified or affirmed via the honor that people show to him. We are warned lest a Rasha be honored or approved in our eyes. We should view his wealth and honor like a gold ring of a pig's snout - the ring does not honor it in our eyes. A leper's wealth does not make people aspire to wealth due to seeing his wealth.