Why does it say "Hinei Shoked Aleihem"?
Malbim: It already said that those who want to go from Eretz Yisrael to Egypt, the general evil that will come to Anshei Egypt will come to them. This adds - I will be diligent to do special evil to them, until they are totally eradicated.
Why will the sword and hunger eradicate them?
Radak (26): This is opposite to what they said - "Lo Nir'eh Milchamah... vela'Lechem Lo Nir'av" (42:14).
Will everyone be eradicated?
Radak: This is an exaggeration. It means most of them, for it says "u'Flitei Cherev" (verse 28).
Why does it say both "v'Samu" and "Ad Kelosam"?
Radak: This is additional explanation and to strengthen the matter.