Yes it is one of the deadliest volcanoes because it can generate really big tsunami waves really easily. Even eruption between VEI 2-4 can do that. I know that one VEI 3 eruption cause tsunami waves there.

It is possibility that there have been big eruptions before that minoan VEI 7 eruption but there is no hard evidence.

One possible reason is that tsunamis have been so big that all evidence those eruptions is now under sea...