Soft magnetic materials are vital for a wide range of technologies. However, the very diversity of these applications poses a fundamental challenge for their design and manufacturing. This is compounded by a typical trade-off: improvements in mechanical property often necessitate a sacrifice in magnetic property, thus hindering the achievement of a comprehensive performance balance.  To overcome this, we present a FeCoNi-based multi-principal element alloy fabricated via dual-powder alternately deposition additive manufacturing (AMed-AD). This approach creates a unique honeycomb-like multistage microstructure with coherent (Fe, Co, Ni)₃Al precipitates. Compared with cast counterparts, the AMed-AD alloy achieves superior tensile strength (528.4 MPa) and elongation (35.4%)―improvements of 150% and 179%, respectively―while preserving magnetic properties due to the refined, homogeneous microstructure that minimizes domain-wall pinning. Corrosion resistance is also enhanced through microstructural refinement and chemical homogeneity. DFT calculations reveal that alloying increases charge localization and interfacial bonding while reducing the density of states at the Fermi level, collectively underpinning the improved mechanical, magnetic, and anti-corrosion performance. This work offers a microstructural engineering strategy to break traditional property trade-offs in soft magnetic alloys.