A 20-foot tidal wave such as Christmas a couple years ago seems to be large. A 20-inch tidal wave such as last month is a laugher. A 200-foot tidal wave 8000 years ago in the Levant would be memorable if anyone survived to carve a note in a rock.
That's quite possibly something that happened about 14,000 years ago with the breakup of the two mile deep glaciation then covering Antarctica.
I think the limit for earthquake induced tsunami’s is about 90 feet or something? (30 meters sounds familiar). But it is based on an earthquake typically has a maximum displacement. Of course the shoreline where it hits factors in as well.
But a tsunami caused by a landslide can be huge as there can be so much more mass displacing the water. There was one up in Alaska on a narrow fiord and a boat was lifted up over a point of land that was hundreds (a thousand??) feet in elevation above the normal water level. The guys lived to tell about it!
Okay - 1700-foot tall wave! The year - 1958.
http://www.sitnews.us/Kiffer/LituyaBay/070808_lituya_bay.html