What's the Most Significant Textual Variation?

The two largest textual problems we have are both 12 verses long and there are some critics who like to speak of them as they're just among several that are lengthy which is not a good representation of the facts. The next longest passage is two verses and we have I think about 15 places where one or two verses are involved. And everything else after that is part of a verse often just part of a word, most variants are just spelling differences or transposition,. But Mark chapter 16 verses nine through 20 is 12 verses long. That's where it speaks about Jesus telling us apostles if you pick up snakes, you will get harmed, drink poison, you'll be fine, you know, all this