As Dusk Falls

To earn this achievement you need Vince to warn Dale about the sniper to avoid him getting shot.

To accomplish this, load up the "Jim or Zoe?" section of the Chapter 2 story tree. You may have different tree paths available instead at this point. We're looking to reach the "Human Shield" section, which is unmissable and results regardless of the story tree you take to reach it. Personally this section got me closest to the relevant section though!

The important decisions which will impact this achievement are as follows:

Once you're outside as Vince, I chose the "You'll get there" option. Shouldn't matter on your choice here, but just to keep him happy!
When the red dot is aimed on Dale's head, select the "Warn Dale" option.

Very simple, very obvious! Your achievement will pop once the resulting cutscene ends.

A video of this achievement can be found in the video below, starting at 4:04.

Near the end of chapter 2 warn Dale when the sniper is aiming at him.

For a Full and Fast Achievements Guide check the link below:


Timestamps:

00:00 Intro + Useful Information
02:02 Chapter 1: Story
03:49 Chapter 1: Code Breaker + Smooth Criminal Achievements
05:14 Chapter 1: Message Received + Tables Turned + And So It Begins… Achievements
06:32 Chapter 1: Bungled Achievement
07:16 Chapter 1: Cop Out + Point Blank Achievements
08:18 Chapter 2: What’s Your Emergency? Achievement
09:12 Chapter 2: Story
10:08 Chapter 2: Paging Dr. Walker Achievement
10:57 Chapter 2: Keeping The Faith + Second Chance + Lifesaver Achievements
11:56 Chapter 2: Dodged A Bullet + Caught in a Trap Achievements
12:21 Chapter 2: What’s Done is Done + Unforgiveable Achievements
13:32 Chapter 3: Long Arm of the Law
14:01 Chapter 3: Story
14:24 Chapter 3: Resurrection Achievement
14:48 Chapter 3: Take Me Instead + New Dawn + From Dusk ‘til Dawn Achievements
15:59 Chapter 3: Better the Devil You Know Achievement
16:23 Chapter 3: Buried Alive Achievement
16:44 Chapter 3: She’s Coming with Us Achievement
17:18 Chapter 4: Invincible Achievement
17:49 Chapter 4: Story
18:46 Chapter 4: Cabin? What Cabin? + Brothers in Arms + Into The Woods Achievements
19:46 Chapter 4: Trail of Breadcrumbs + Once a Holt + Hands in the Air + No Going Back Achievement
21:19 Chapter 5: Bullseye Achievement
22:04 Chapter 5: Plead the 5th Achievement
22:28 Chapter 5: Story
22:54 Chapter 5: Jailbird Achievement
23:23 Chapter 5: Heart to Heart + Bonnie and Clyde + Runaways Achievements
24:14 Chapter 5: Cuba Libre Achievement
24:58 Chapter 6: Story (Wait for the Cop)
25:43 Chapter 6: Into the Wild + Breaking Bread + Past, Tense + End of the Road? Achievements
26:56 Chapter 6: Almost Made It + Enough is Enough + Stay of Execution
27:47 Chapter 6: You’re On Your Own (Chapter5) + Free Bird + Most Wanted Achievements