The most dangerous thing about calculating gambling probabilities is 100% certainty. Experience tells us that you can never be 100% sure of any near-probability. On the other hand, if we move from bookmakers to prediction platforms, you can indeed find extremely unlikely events there. For example, the second coming of Christ. What percentage would you rate the probability of such an event? I would estimate it at 0%. And when it comes to football matches, I'm almost never 100% sure of anything.
On prediction platforms (such as Polymarket), in addition to the wording of the bet terms themselves, you should also carefully read the additional conditions under which the bet is considered a winner or loser. 🙋
For example, a bet might be worded like this: "Aliens will visit planet Earth by January 1, 2027." The additional conditions under which the bet is considered a winner or loser might read: "The bet is considered a winner if one of the leading American newspapers publishes the relevant information." In my opinion, this contains a serious logical trap. Consider the following scenario: Suppose the editor of the relevant newspaper learns of the bet and publishes an ad, for example, in the "Humor" section. And technically, the bet wins!
Therefore, in my opinion, one should always be very careful when claiming that a bet will win or lose with 100% probability. For me, the expression "100%" is an absolute no-no. I never use this in either written or spoken language. The only expressions worse than this are "120%," "150%," and so on (applied to the probabilities of various events). I don't even talk to people who say this. If I hear something like this, I immediately get up from my chair and leave the room. I realize that this person is either an idiot or thinks I'm one. And I don't like that. 🙅