play hardball

play hardball (be extremely competitive often in an unfair manner; act aggressively and ruthlessly) — занять жесткую линию, занять бескомпромиссную / непримиримую позицию (особ. в политике); действовать жестко, бескомпромиссно, возможно, силовыми методами; ≅ пойти на принцип

hardball (forceful uncompromising methods employed to gain an end) — жесткость, бескомпромиссность, несговорчивость

Example: If the boss wants to play hardball, show her that you are tough.

...He glanced down at her with a smile, and gently kissed her full on the lips, as he continued listening to his boss without missing a beat for a moment. And then he gently pushed her away as he went on talking. "That's right... that's what I told him. They said they'd get back to us next week, but I think if we play hardball with them we'll get them to come around before that. Right... right... that's exactly what I think... fine... see you in the morning." (Danielle Steel, "Heartbeak")

......Luis said to Eddie, seated by the window. "You don't want me trash-talking another Biodyne fighter, but I thought you wanted us to apply some pressure." The shallow lines on Eddie's forehead deepened with a grimace. "You did, by routing Hadrian. You'll be number two at worst in the next rankings. Biodyne won't want to lose a rising star. They'll give us that contract extension on our terms, and that includes a title shot." Luis nodded slowly. "If you say so, but playing hardball with them still doesn't feel right." An ungainly smile made him look even younger than his twenty-three years. "Talking about myself and other fighters is part of the game. That comes naturally, but I've got no reason to hold Biodyne's feet to the fire. I've been with them my whole career." "You're talking about sentiment, Luis, but they're acting on business. Give them an opening, and they will exploit you." (Shane Tourtellotte, "Nanoweights")

This term originated in baseball, where it alludes to using the standard ball as opposed to the slightly larger and minimally softer ball of softball. It was transferred to describe aggressive behavior only in the 1970s. (The American Heritage Dictionary of Idioms)