Season 2 expanded the universe without breaking it. We saw the genesis of the Canary (Caity Lotz) and the introduction of Barry Allen (Grant Gustin) before he became The Flash. But the heart of the season was the brotherhood between Oliver and Slade, juxtaposed with their present-day rivalry. The mirakuru serum plot gave us super-strength soldiers, raising the stakes from street-level crime to biological warfare.
This is the The Dark Knight of the Arrowverse. Essential viewing. DC Arrow Season 1 2 3 4 5 - threesixtyp
(Deathstroke) arrives in Starling City, fueled by a Mirakuru-induced vendetta and the death of Shado. Team Expansion: Season 2 expanded the universe without breaking it