Phishing attacks can be mostly avoided because most of the phishing websites looks very different from the original websites (there are exceptions to). So it’s much easier to avoid such attacks easier.

Data breaches are a little more scarier according to the amount of important data you have within you. It’s highly effective for larger companies who depends on digital data, and breaching them would bring a lot of damage to their company.

But ransomwares are the deadliest among these. It not only holds on to our data, but also asks ransom for freeing the data, and even can take control on the target system. The most scarier part is that everything happens under the hood, so we can’t even see or block what’s happening.

So for me, Ransomware‘s are the most deadliest among the options that you have given.