AlphaGo defeated the world's best Go player in 2016

In March 2016, DeepMind's AlphaGo beat 18-time world Go champion Lee Sedol four games to one — a decade ahead of most expert predictions. Go has more possible board positions than atoms in the observable universe, making brute-force computation impossible; AlphaGo used deep reinforcement learning to develop intuition rather than calculation. After the defeat, Lee Sedol said the experience made him feel 'a little bit detached from reality'. He retired from professional Go in 2019, citing AI as an unconquerable opponent.

Source: Silver et al., Nature (2016)