This mod for Black Mesa lets you take on the role of the villains and come face to face with Gordon Freeman himself
Black Mesa: Military has finally seen the light of day. The fan-made mod, which has been in development since 2018, allows players to stand on the other side of the barricade and take on the role of one of Half-Life series protagonist Gordon Freeman's opponents.

Are you tired of playing 'the good guys' in games? If so, I have a proposition worth taking a closer look at. I'm talking about a modification titled Black Mesa: Military. This fan project has finally been released and can entertain players while they wait for the official announcement of Half-Life 3, which – judging by the latest clues – is probably only a matter of time.
The story goes like this: you are not a survivor, you have been sent on a mission. Secure the Black Mesa research facility with the rest of your squad and eliminate any hostile forces. You will experience the disaster in Black Mesa from the perspective of the H.E.C.U., and you will even see Gordon Freeman in person
If some of you are experiencing a sense of déja vu while reading the game description, don't worry, because Black Mesa: Military is a modification based on a similar idea to Half-Life: Opposing Force. Following the example of the official expansion, the mod allows us to take on the role of one of the marines who were portrayed as the main character's enemies in Half-Life. The story and maps in Black Mesa: Military are completely new though, they’re not in any way based on Opposing Force.
According to the information on the project's website, work on it began back in 2018. The original plans of the authors included a simple map pack for Black Mesa,' but over time the modification has grown to much larger proportions. Interestingly, the creators assure that this is not the final version of Black Mesa: Military – further improvements are planned for the future. Below, you can watch the project's trailer.