An air carrier pilot reported another aircraft taxied on to the wrong taxiway and passed within 50 feet of their aircraft.

Narrative

Landed 12L. Tower controller handling multiple frequencies. Tower instructed E; H; hold short of 12R. Eventually cross 12R; then taxi D; C3; C to the gate. At one point Aircraft Y was moving parallel with us in a northwesterly direction on C whilst we were on D. Aircraft Y was instructed C4 then cross 12R. As we were about to turn left onto C3 as previously instructed Aircraft Y disregarded our instruction and our presence on the taxiway; and taxied at a very unsafe speed violating their own instruction to take C4 and they entered C3 and then proceeded take J; cutting dangerously close in front of us (estimated within 50 feet of our aircraft) and forcefully taking the remaining left side of D to join J. Captain questioned TWR and did not get a response; this created an extremely unsafe situation added to which ATC did not elect to impose a safety stop to inquire and remedy. TWR instructed us to stop and Aircraft Y to expedite.Tower was responsible for causing a near ground collision and potentially an incursion (incursion upon liability of the other aircraft; by TWR disregarding our position) with regards to the loss of situational awareness the controller had over there primary function to ensure safe ground position and movements of both aircraft). At one point whilst continuing to our gate after that; TWR ignored when I questioned how and why this happened; TWR disregarded my communication and made it appear as if Aircraft Y has ATC supremacy. Thereafter controller had the audacity to ask us to expedite for another Aircraft Z behind us; to which I declined evident that the controller was attempting to cut corners in safety I did not rush and did not compromise any measure of safety.Background info - at this point in time CA was PF for the purpose of being the pilot taxiing the aircraft. PF on the ground. CA did takeoff; transferred controls to FO; FO conducted landing at CA's delegation due to MFD (Multi-function Flight Display) #1 failure in-flight.Cause: ATC safety margins comprised.Suggestions: ATC may consider this as a learning experience to avoid a repeat.