Manhwa(?) where the female lead dies and returns to her wedding night

Question

I don't know if it is a manhwa, manhua or webtoon. It is full-colored and this is the synopsis:

It's set in a historical, European era with nobles, etc. The female lead is a noble with an over-powered wizard sister. The male lead is a noble of a plagued territory. (It's possible he has black hair.)

The female lead (noble) got into a loveless marriage with the male lead (noble). He isn't home for years because of war and she suffers from her stepmother's abuse.

After her husband comes home, he is even colder. His territory declines more and more until the emperor suddenly accuses the husband of treason.

The husband pleads for the life of his wife because she is pregnant but she still gets killed by the emperor's sword.

She starts at her wedding night again and changes her life.

The first thing she does is get her husband to stay. Afterwards she stops her stepmother from using her money and invests it into the territory. With the knowledge of her previous life, she tries to change the direction of the territory.

She also reconciles with her family a bit, which is how the reader knows why she got married instead of her sister.

Answer 1

This is Leveling Up My Husband to the Max. It is available for free on Webtoons.

A cold, uncaring husband, and unreasonable mother-in-law, and a wrongful death — could your life get any worse? What if you were given a chance to change things? When Amber is sent ten years back in time at the moment of her execution, she finds herself face to face with the younger version of her husband, but something’s different about him... He’s completely at her beck and call! Will she be able to prevent the past from repeating itself, or will her life spiral into misery once again? Operation: Leveling Up My Husband to the Max begins now!

The story opens with her being executed, while mentioning that she is pregnant with her husband's child.

Then there's a flashback that explains what happened, which matches the details in the question. She is married off to a man who is frequently out on monster subjugations. The territory is barren and harsh, while she's from a more prosperous area. The stepmother in the question is her mother in law (i.e. her husband's mother), and she indeed wastes money.

Her husband is accused of treason and they are both executed. Her husbands pleads for her life, but they both die.

At the end of the first chapter she returns to the day of her wedding.

Answer 2

Leveling Up My Husband to the Max seems to match your description.

From Baka-Updates:

A cold, uncaring husband, and unreasonable mother-in-law, and a wrongful death — could your life get any worse? What if you were given a chance to change things? When Amber is sent ten years back in time at the moment of her execution, she finds herself face to face with the younger version of her husband, but something’s different about him... He’s completely at her beck and call! Will she be able to prevent the past from repeating itself, or will her life spiral into misery once again? Operation: Leveling Up My Husband to the Max begins now!

Due to an imperial order from the Emperor, Amber Lite, is sent to a cold territory in the East to marry Duke Calix Thalesdo, a man she's never met. In reality, the order stated that Amber's sister, Natasha, was to marry Calix, but because Natasha was gifted with magical powers, Amber's father sent Amber as a substitute.

Amber doesn't see Calix during most of their marriage, as he spends that time fighting in various conflicts, leaving her at home with his greedy mother, who used Amber's dowry to buy jewelry for herself. When Calix eventually comes home, he's mentally scarred by war and isn't loving towards Amber, although they conceive a single child together. In the end, he's accused of being a traitor by the Emperor, and Amber -- still pregnant with Calix's only child -- dies by the Emperor's sword. Before Amber's death, Calix had pleaded that she be spared, mainly to save his child.

Amber then wakes up ten years earlier, on the night of her wedding, and decides to become much more assertive and proactive than before, in order to steer her marriage and life in a better direction. She convinces Calix not to head off to war, prevents his mother from getting her hands on the dowry, and helps solve problems (such as a food shortage) in his territory. She also eventually reconnects with her father and sister.

The manhwa is available to read on Webtoons.