Berserk (1997 TV series)
This is the first adaptation and covers the Golden Age arc of the manga. It's a good starting point and provides essential backstory.
Berserk: The Golden Age Arc
This trilogy of movies provides a condensed version of the Golden Age arc.
Berserk (2016 2017 TV series)
These two seasons follow the Conviction and Falcon of the Millennium Empire arcs respectively.
Berserk: The Prototype (2013)
This is a short adaptation of the manga's prototype chapter. It's optional but can provide some interesting insights into the early development of the series.
Berserk (2018)
This is a continuation of the 2016-2017 series and covers the Fantasia arc.
BersBerserk: Sword of the Berserkerk (2018)
This is not an anime, but it's worth mentioning as it follows the story of Guts and expands on some events not covered in the anime adaptations.