UBCS is an acronym for "Umbrella Biohazard Countermeasure Service," the members of which are mercenary characters, often with a criminal background, from the Resident Evil video games. In the games, the UBCS is a special forces military unit maintained by the Umbrella Pharmaceutical Corporation that performs dangerous rescue missions during "biohazard outbreaks." You can create a basic UBCS costume fairly easily, adding various parts and details depending on your resources or budget.
Fashion the basic UBCS costume using black articles of clothing, including a black T-shirt, black flak jacket, black or dark camouflage trousers, black knee pads, a black helmet and black combat boots.
Create your own flak jacket from a black vest (see Resources for examples); flak jackets are vestlike, sleeveless pieces of body armour designed to prevent shrapnel and similar things from harming soldiers.
Make two UBCS logo patches: a larger one for the back of the flak jacket and a smaller one for the front. The easiest way to create them is to paint the logo onto a square of black fabric. Glue or sew the patches to the appropriate spots on the flak jacket.
Enhance your costume with additional details, such as gas masks, shields, imitation rifles and pistols, elbow pads, and so forth depending on materials that are handy and your budget. Examine photos of others' UBCS costumes in various cosplay photo galleries, and see Phoenix Rising's list of "Screen Accurate Components for the Carlos Olivera Costume" (see Resources; registration may be required) for more ideas.