Why does Hashem "Yotzer Ohr"?
Rashi: This is for Tzadikim.
Malbim: Beri'ah is creation of the matter; Yetzirah pertains to varying properties that apply to particular forms. If light was a Beri'ah without varying properties, there would be no room for darkness.
What do we learn from "u'Vorei Choshech"?
Rashi: This is for Bavel.
Radak: The verse mentions Ohr and Shalom, and their opposites, Choshech and Ra. The verse mentions forming and making light and Shalom, for they are actions, and Borei for darkness and evil, which are merely removal of light and good. Borei is a decree, like "v'Im Beri'ah Yivra Hashem" (Bamidbar 16:30).
Radak citing his father: This refers to the land. It causes darkness in the world when the sun sets and the land covers it.
Bechor Shor and Chizkuni (Bereishis 1:2): This teaches that darkness is a creation. It is not merely the lack of light.
Malbim: Even though darkness is merely lack of light, the verse calls it Beri'ah, for it is uniform; its properties do not vary (refer to 45:7:1:2). The same applies to Ra, which is absence of good. Also, via making light and good with limitations (they will not always apply), He created darkness and evil.
What is the significance of "Oseh Shalom u'Vorei Ra"?
Rashi: "Oseh Shalom" is for Tzadikim, and "Borei Ra" is for Bavel.
Radak #1: Refer to 45:7:2:2.
Radak #2: Hashem makes Shalom between these four matters with opposite natures. The body is healthy when there is Shalom among them. If one overpowers its colleague, e.g. cold over heat or heat over cold, or moist over dry or vice-versa, this is illness, which is Ra. This comes from harmful foods, e.g. eating too much food with one of these natures. Or, illness comes from other things. Even though man caused illness to himself, Hashem created them. He did not create them for evil.
Why does it say "Ani Hashem Oseh Chol Eleh"?
Radak citing Rav Sadya Gaon: Good and evil are attributed to Kel's creation. This counters one who believes in two Powers, one good and one evil.
Malbim: Also darkness and evil are due to Shem Hashem (existence and good). His Chachmah decreed that this is the only way for good to be revealed. Moreh ha'Nevuchim (1:73, 3:10) and Sefer Emunos of Rav Sadya Gaon (1:4) explain this.