I hesitated to count this game as a series because after the Super NES you don't hear much about it, but with 3 games on NES and Game Boy and 2 on SNES (even though I wish the 5th had never come out) + a crossover with Battletoads on each of those consoles, it is still a major series.
If you only play one, play this one. Double Dragon 2 - The revenge is a model of the beat 'em up and this NES version is a success. Beyond the walkthrough, I also made some YouTube playlists:
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