EMB-145 First Officer reported they had to aggressively brake to avoid another aircraft which taxied across their path.

Narrative

The event occurred while taxiing on the ZZZ ramp around D concourse. We were cleared by the east ramp frequency to taxi from our present position (pushed back off or EX) to spot 24X and contact the south ramp frequency. Immediately after receiving our clearance; an Aircraft X was cleared to make a right turn to spot 25X and contact Ground. Approximately a minute later; while rounding the corner from the north to south west; near spot 26 we had noted that there was an Aircraft Y that was stationary off to our right; further down the D concourse near gates D3 or D5. Shortly after passing spot 26 the Aircraft X turned out and proceeded immediately in front of us with no apparent regard for our direction of movement. Our Captain had to aggressively brake to ensure we would avoid the aircraft. Throughout this whole time; there was no communication from either the Aircraft Y; or the Ramp Controllers on involving any potential traffic conflicts on the ramp or having either us; or the Aircraft Y stop to avoid the conflict.