What does the Pasuk mean when it states that Bil'am saw Amalek?
Rashi: It means that he saw the punishment (downfall) of Amalek.
Ramban, Rashbam and Targum Onkelos: It means that he actually saw Amalek from the vantage point where he was standing. 1
See Ramban.
Why does Bil'am refer to Amalek as "Reishis Goyim"?
Rashi, Ramban #1, Rashbam and Targum Onkelos:: Because they were the first to attack Yisrael 1 (after they became a nation). 2
Ramban #2: Because they were a leading power among the nations. 3
See also Ba'al ha'Turim.
And ultimately, Yisrael will destroy them, as the Pasuk states in Devarim 25:19 "Timcheh es Zeicher Amalek".
Ramban: Due to their great strength and fighting ability, as is evident from the battle against Yisrael, recorded at the end of Beshalach. See Ramban.
What did Bil'am mean when he concluded "ve'Achariso Adei Oveid"?
Rashi: He meant that ultimately, Yisrael will destroy Amalek. 1
Ramban and Seforno: He meant that 2 , although they are a mighty nation, 3 they will perish more than any other nation. 4
Targum Onkelos: He meant that, ultimately, they will be destroyed forever'.
Targum Yonasan: He meant that, ultimately, in the days of Mashi'ach, they (Amalek) will join forces with the nations of the east to wage war against Yisrael; and they will all be destroyed forever'.
Rashi: As the Torah writes in Ki Seitzei Devarim, 25:19 "Timcheh es Zeicher Amalek!" Rashi in Koheles (8:9): 'I saw and I took to heart ... how a person dominated his friend and overpowered him, and how ultimately, it turned out to his detriment: Amalek overpowered Yisrael, but in the end "ve'Achriso Adei Oveid" - and that is what happened to Par?oh, Nevuchadnetzar and to Sancheriv'.
Seforno: ?Even though all nations will be destroyed in the time of Mashi?ach ? a remnant will remain ? with the exception of Amalek ? the first to attack Yisrael, and Kitim (Rome - in Pasuk 24) ? who completed the destruction of Yisrael, as the Torah writes there ?ve?Gam Hu Adei Oveid?.
Ramban: As the Torah writes in Sh'mos 17:14 - "Ki Machoh Emcheh es Zeicher Amalek!"
