GWENT: The Witcher Card Game

To get this achievement, you have to:
1. Lose by 20 points in any of the 3 rounds.
2. Win the game.

I lost by 20 points in Round 2, while losing, and won Round 3. Achievement unlocked!

Here's the deck I used, made by velen_rendlich on Gwentup: https://gwentup.com/decks/45 .

In text:
The deck is not made specifically for this achievement and I think you can optimize it more. Two changes I would do, are:
- Weavess: Incantation + Naglfar
- Wild Hunt Navigator + Alpha Werewolf

There are two main cards in this deck that will help you get this:
Count Caldwell: "Every turn, on turn end, move to the row with the highest unit on the battlefield". This means that if you have the highest unit (with Caldwell), he will stay on your side. But if your opponent plays a higher unit (10+), Caldwell will move to the opponent's side at the end of your turn. This is what you want! See guide further down below.

Mourntart: The MVP and main win condition of the deck. Will usually net you 20+ points in the last round. Must be played when you have two cards left (as it has order), and should be combined with Eredin's ability (make unit immune). This will make sure that you get a lot of points last round and often win because of it..

How to do it:
I didn't specifically go for this achievement and played ranked while I got it. But I recommend Casual for less "tryhard" players. You will need to get lucky, both to get an opponent that has high power cards (making sure you fall behind 20 points) and that he lets you play the final card (and activate Mourntart) last round.

Round 1:
Mulligan phase: Make sure you have one Wild Hunt Rider, one of the witchers, and no Roach.
If on blue coin; play Wild Hunt Rider (to thin your deck), if on red coin; play Wild Hunt Rider if it will be the highest unit.
Start by playing Thrive cards (Nekkers, Archespores, and Drowners). Thin your deck with Wild Hunt Riders (if not played already), and Witchers (Eskel / Vesemir / Lambert). Usually, you can play down to 5-6 cards. You want to play as long as possible and ideally win, without losing card advantage (going two cards down).

Round 2:
Cards you want on hand: Mourntart and Count Caldwell, if one of them is in the deck you want Naglfar. The rest of the hand could be Crones (Whispess, Weavess), and relict horses (Chironex, Unicorn).
If you lost first round, pray that opponent passes and doesn't bleed you. When opponent tries to bleed you, play strong cards only. It's okay to be even in the last round!

If you won the first round, you want to play on. Try to play down to 2-3 cards, while keeping Mourntart, or Naglfar in hand.
PLAY Count Caldwell right before you want to pass, while still keeping the lead. This will likely bring the opponent's total power to +20 (if he steals Caldwell) => losing by 20 points.

Round 3:
Try to maximize the points on each card in your hand. Make sure to keep Mourntart and 1 other card until you have 2 cards on hand. Play Mourntart (ideally on a row with less boosted units), and use Eredin ability on it to make it Immune and 4 power. End turn. Play last card and activate Mourntart's Order and it might be enough.

I did record the last turn, when I got the achievement, but not getting the achievement. If you want to see it, I could add it to the solution!