Using a 400 μJ ytterbium laser combined with a novel pulse compression technique, we demonstrate a state-of-the-art terahertz (THz) source from the tilted-pulse front pumping scheme in lithium niobate at room temperature with record efficiency of 1.3% capable of generating 74 mW of average power and 400 kV/cm at focus. Key points of this demonstration include the use of a pump pulse duration of 280 fs in combination with a stair-step echelon mirror and an off-axis ellipsoidal mirror. This source has unmatched characteristics of generating intense and powerful THz pulses at the same time and remains highly scalable as compared to existing Ti:sapphire-based THz sources pumped in the millijoule range.