The best champions globally to counter 炼金术士 include 祖安花火, 复仇之矛, and 探险家. These champions are all good at countering 炼金术士 with high win rates over 55%. Even if these 炼金术士 counter picks are not picked in your lane, it's not a good idea to play him into these matchups. They will often beat 炼金术士.
Yet, if the enemy team brings either 迅捷斥候 or 星籁歌姬, 炼金术士 mains should strongly think about selecting him, as he easily wins against these selections with win rates over 57% against both ofthem.