Chaos / Constance Fay.

Enhanced descriptions from Syndetics:

Lore Olympus meets Winter's Orbit in this pulse-pounding romance between a space mercenary and a super soldier whose mind-control breaks when she touches him.

He's a mind controlled killing machine, until her touch frees him

Engineer Caro Ogunyemi thinks she has everything in control. Sure, she has a dark secret in her past and aim so bad that she can't shoot the side of a spaceship when she's right in front of it, but those are minor details in the life of a space mercenary. When Caro embarks on a solo mission infiltrating a prison planet that is run by the deadly Pierce family, she embraces the opportunity to prove she's a hero.

It's there that Caro meets Leviathan, a super soldier with a chip in his head that turns him into a mindless killer. He's drop dead gorgeous with an emphasis on drop dead, until she touches him and renders his chip inert. The danger begins when she lets him go.

In the heart of enemy territory, where love is at stake, life is treacherous and time is short, Caro and Leviathan must figure out how to recover his agency, protect her crew from Pierce's sinister machinations, and stage a prison-break before Leviathan is lost to her--and himself--forever.

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Kirkus Book Review

A tech genius falls for a man who was turned into a genetically enhanced supersoldier against his will. Caro Ogunyemi works as an engineer aboard the spaceshipCalamity, and there isn't a piece of tech she can't operate, repair, or hack. While her crew is on leave, she accepts a job to infiltrate Shikigami, a luxury prison planet for wealthy criminals operated by the Pierce family. Her mission is to find evidence that Carmichael Pierce has a secret lab at the prison where he's using stolen tech to build supersoldiers out of unwilling test subjects. Caro's shameful secret is that she worked for Pierce a decade ago, and she suspects some code she developed and attempted to destroy might be part of the supersoldier protocol. Once on planet, Caro learns that most of Pierce's attempts to create supersoldiers have failed, with the exception of a terrifying specimen they call Leviathan--and her bungled attempt to infiltrate the prison puts her into a face-off with him. During the life-or-death fight, Caro discovers that her touch deactivates Leviathan's chip, which allows him to reason and think for himself as long as she can keep her hands on him. Caro feels instantly attracted to Levi as his real self, and he feels a similar pull, calling her "angel" and begging her not to abandon him. Caro is charmed by the man behind the programming and vows to save him. With the help of two undercover friends, Caro makes a plan to destroy all of Pierce's records and extract Levi. Everything that can go wrong does, leading to a series of high-stakes and at times hilarious adventures. Caro is a robust, interesting character, and her sweet romance with Levi allows her to forgive herself for past mistakes. The gang's adventures on the prison planet are a rollicking good time, with complex, fast-paced plotting and intricately choreographed action sequences. A wildly entertaining space adventure explores the nature of love and humanity. Copyright (c) Kirkus Reviews, used with permission.