NOTHING

Hello MoH

As you say, it does in fact mean 'never saw anything like
this'. The double negative is used in very informal
speech to add emphasis, e.g.

'You ain't seen nothing yet' [= you have not seen anything yet]
'You ain't nothing but a hound dog' [= you are nothing but a hound dog]
'You ain't going nowhere' [= you are not going anywhere]
'I never saw no one' [= I didn't see anyone]

This shouldn't be confused with the literary double negative,
where the negatives cancel each other out, e.g.

'It cannot be said that I am not a patient man' [= 'it can be
said that I am a patient man'].

To decide whether a double negative belongs to the first or
second kind, you have to look at the context (e.g. is this the
kind of person who would use an emphatic double negative?).

There ain't no other way, unfortunately.

MrP