What is the WORST ending?

[Exarch_Alpha]

I got Suzuha´s so if its the one then I´ll play the game again.

[DPM JaMaN]

There are few similar endings to Suzuha's, those are called alternative endings, not bad. One of the worst endings in my opinion is Lukako's.

[Runa Silvertongue]

I haven't gotten Mayuri's or the true ending, but Kurisu's ending killed me emotionally.

[Exarch_Alpha]

Gotcha but what is canonically the WORST ending?

[DPM JaMaN]

There's no such thing) True ending is the most canonical thing you can have in S;G.

[Exarch_Alpha]

But to play the sequel which ending I should get to make the most sense of it?

[DPM JaMaN]

Zero is not a sequel, it's a so-called interquel. It's events do hapen during main game and lead to the true ending. There were lots of threads here about the best order and how to combine S;G and S;G 0 in a single experience, search 'em up if you're into it.

[Exarch_Alpha]

Ok will try to get a new ending here then move to Zero

[Atlantean: Ascended Observer]

You should get the true ending before Zero

[Exarch_Alpha]

Ok two more questions:

1- Do I have to replay it to get new choices, like in Undertale?
2- which chapters are most important for the endings? Prologue counts? Also no spoilers, I just want to know which chapters so I can look for clues.

[tricosahedron]

Originally posted by Exarch_Alpha:

1- Do I have to replay it to get new choices, like in Undertale?

Technically, you have all options from the start, but the game indicates when you have an option once you reached an ending for the first time.
(starting over not required; you can simply load an old saved game)

Originally posted by Exarch_Alpha:

2- which chapters are most important for the endings? Prologue counts? Also no spoilers, I just want to know which chapters so I can look for clues.

Except for the true ending, the choices you have to make to avoid a side ending should be not too far in the past; same chapter or previous chapter, I think, but not sure. You'll quickly get a feeling for this once you figured out how to avert the Suzuha ending.
The true ending is much more complicated, though.