What is the meaning of "v'Sikarti"?
Rashi #1: This is like v'Sagarti (I will hand over). Radak - this is like "Yesagercha Hashem b'Yadi" (Shmuel I, 17:46). Also Yonason translates v'Emsar.
Rashi #2: This is like "va'Yisakru Kol Maynos Tehom" (Bereishis 8:2) - I will seal and bind it.
Will Egypt be handed over to many masters?
Rashi: No. "Adnus" is always plural, even for one master, e.g. "Adonei Yosef", "Ad Bo Adonav" (Bereishis 39:20, 16).
Radak: No. Adonim is a glorified expression for an individual, like "Im Adonav Yiten Lo Ishah" (Shemos 21:4).
Malbim: Yes. Many cruel masters are worse than one cruel king, who cannot put his cruelty on so many individuals, only on the Klal.
Who is the fierce king?
Rashi: It is Melech Ashur. Radak - it is a repetition of "Adonim Kasheh."
Malbim: He is over the masters, so they have no hope of casting off their yoke; the king will strengthen their rule.
Why does it say here Ne'um Hashem?
Malbim: Until here, the Navi heard Hashem speak. From here and onwards, the Navi himself speaks.