Well that's going to be subjective, usually in the past I see most guys here don't want to answer this with any real effort. Meaning they just tell you that first bit I said, "No way to know until you try them." Or "they're all exactly as toxic as each other but how your body takes them is what makes them more or less dangerous."
I think all that stuff is hogwash, why else would anavar be considered safe for children? Medically, there IS a difference in toxicity. But these lists will be based on opinion.
The least toxic oral is Anavar, by a landslide. Here's a list of some common ones from most to least toxic, in my opinion.
Methyl Trest (Cheque Drops)
Methyl Tren
Methyl 1-T
Superdrol
S23
Methylstenbolone
Desoxymethyltestosterone
M1,4ADD
M1-AD
Dianabol
Epistane
Dymethazine
Winstrol
Yk11
Dimethandrostenol
Methyldiazirinol
Anadrol
Ostarine
LGD4033
Anavar
In my experience, high toxicity does not equal high side effects.
All of these have the ability to give great results provided they are used in the context of their best functions. You wouldn't want to try and bulk up with epistane, for instance. Methyl 1-T, however, shines with a raging fury on a bulk.
Here's a list of most to least side effects in my experience
Anadrol
M1,4ADD
Dianabol
Superdrol
M1-T
Yk11
Epistane
Methylstenbolone
M1-AD
Winstrol
Dimethandrostenol
Desoxymethyltestosterone
DMZ
No sides whatsoever
Methyldiazirinol
Anavar
Ostarine
LGD 4033
Again, these are my experience and opinion.