@Jo191, I haven't really had a lot of 'nightmare' guests, but a few that clearly haven't read the listing properly or brought additional people. I think some of your 'deal breakers' would probably apply to heaps of my guests who have turned out to be wonderful! To respond to your list:
Obvious Deal Breakers:
1. No Reviews: doesn't bother me - everyone has to start somewhere.
2. No Picture: I would prefer to see a profile photo and will often ask them to upload one if they don't have one. But it's not a deal breaker.
3. No Verification: You can set up your listing so that guests must be verified before they can book. https://www.airbnb.com.au/help/article/272/can-i-require-guests-to-be-verified-before-booking
4. Bad Review(s): I would read the reviews and take them in context of other reviews. A very bad review would definitely raise alarm bells for me and probably be a deal breaker.
Additional Deal Breakers:
5. Asks for a discount: yes, this does raise alarm bells for me but I just say no discounts as my room is already very cheap.
6. Asks to for an early check in and/or late check out/hold luggage, etc.: usually I just explain that I need time to prepare for the next guests so early check in or late check out is not possible. But I will accommodate early check ins on occasion for people who really need it. It really doesn't bother me if they ask politely and I can just decline if it doesn't suit. Definitely not a deal breaker.
7. Asks to bring more than the maximum guests: this has happened a few times but I've just declined as I cannot accommodate more than 2.
8. It becomes clear they have not read the house rules: this would apply to probably 50% of my bookings! I send all booking requests and Instant Books a message asking them to make sure they have fully read the listing and house rules, then explain that I have a flexible cancellation policy if they don't think it is a good fit for them. I also have a guest manual in the room with a brief list of the important house rules and ask them to read it on arrival.
Deal breakers for me are people with very bad reviews or who want to book and are clearly going outside the listing description i.e. have more than 2 guests or want to bring young children.