As tahmkench, Go for regular burst trades against him, preferably from within the minion wave. It will keep you safe from Tahm's all-in potential.

Tahm has a decent amount of mobility built in his kit so make sure that you don't waste your dash freely.

You are way more tanky than Tahm in this matchup so use this property to safeguard your allies. Failing to do so can easily get your backline killed.

Keep an eye out on your allies in this matchup. If you see someone is low and in a skirmish, ult them immediately if the fight looks salvagable. As tahmkench, It will keep you safe from the total potential of Tahm. Tahm has a good amount of mobility built in his kit so make sure you don't waste your dash freely. You are much more tanky than Tahm in this matchup so use this property to protect your allies. Do not do it easily can get your backline killed. Keep an eye on your allies in this matchup. If you see someone is low and in a skirmish, then immediately if the fight seems healthy.