Supersampling (SSAA)
The brute-force anti-aliasing method — render the whole image at a higher resolution, then shrink it so jagged edges average into smooth ones.
SSAA (supersampling anti-aliasing) samples each pixel's colour several times by literally rendering more pixels — 2× per axis means four times the shading work. That cost is why it lost ground to MSAA, which supersamples only at geometry edges, and later to FXAA and TAA, which fake the result far more cheaply.
Its quality is still the reference the cheaper methods are measured against, because it anti-aliases everything — edges, shader aliasing, thin specular highlights — not just silhouettes. It survives as a downsampling option (DSR) for players with GPU headroom, and modern temporal upscalers are in part an attempt to reach SSAA-like results without the price.