All appearances of the Borg (arguably the most exciting adversary in the franchise) in Star Trek.
Ranked by in-universe chronological order. Exception: Most of PIC S2 takes place in 2024 (time travel), but watching it first does not make much sense. In DS9 1x1 and 1x2 the Borg appear only in Flashbacks. In VOY 4x18 and 4x19 a photograph of a Borg is shown. In LDS 1x2, 1x9 and 2x8 the Borg appear only as holograms. In LDS 3x3 the Borg snake appears as a nightmare come to life.
Source: https://memory-alpha.fandom.com/wiki/Borg#Appearances
Source for chronology: https://startrekviewingguide.com/
Top 50 episodios Star Trek DS9
by Garrac el Saqueador