Tahm Kench vs Olaf Top Matchup
Tahm Kench Top wins 53.3% of 533 Low Elo games against Olaf Top, +1.2 points vs expected, 2-patch window 26.19-26.20.
Researched on LoL patch 26.20. Tips are written to hold at any rank; stats come from Low Elo ranked games up to patch 26.20.
How to play as Tahm Kench
Keep Abyssal Dive(W) to escape when Olaf activates Ragnarok(R); do not dive onto him while his R is available, and look to re-engage after it ends.
Use Tongue Lash(Q) and a Grasp attack for short trades, then back away instead of committing to a long fight while Olaf's R is up.
While Olaf R is active and he keeps attacking, he is immune to disables, so Tahm Kench Q's stun and W's knockup cannot stop his advance.
Sources
These notes come from r/Tahmkenchmains, checked against the champions' abilities.