[PC] [1990-2000] First-person shooter in a space facility with a gigantic mantis-looking alien in a green cylindrical vat as a bossfight

Depending on which path you take, you either fight a gigantic mantis-looking alien in a green cylindrical vat or a huge flesh-colored monster with two small beady eyes and a sad-looking face in a really small tunnel where you are constantly backing away from it. There's a bomb button you can use to deal a lot of damage to the boss but it's limited