MySQL sort varchar as number issue

MySQL sort varchar as number issue

I have seen lots of question like this on SO and I tried to implement the
answers into my particular situation but I am having no luck. Some help
would be greatly appreciated.
Query
SELECT `avatar` from `users` ORDER BY ABS(`avatar`) ASC;
Result
+--------------------------------+
| avatar |
+--------------------------------+
| 0/1_default.jpg |
| 1/3_483487-1440x900_qp8a5a.jpg |
| 1/122_default.jpg |
| 1/321_default.jpg |
| 1/25_wefvvv.jpg |
| 1/1000_latest.jpg |
| 2/12_wefwefwef.jpg |
| 2/1_default.jpg |
+--------------------------------+
I tried to sort by ABS and columns but unless I made a new column or a
dedicated table, I cannot find a way to sort this the way I want it to.
Essentially, I want to sort it numerically and a desired outcome would be
something like:
Desired result
0/1
1/3
1/25
1/122
1/321
2/1
2/12
From the searches on SO, I know there is the SUBSTR function but with the
'/' in the middle, I am not sure how I can get it to sort properly.