Run-On sentence or not?

Yes it is. Put a period after exhaustion.

It is not a run-on sentence, but… it has no punctuation… I suggest:

The truly astonishing aspect of it all is how Alec disregarded all morality, and took full advantage of the state of exhaustion Tess was enduring, that one night in the shielded woods.

how about: the truly astonishing aspect of it all, is how alec disregarded all morality and took advantage of tess’s exhaustion that night in the shielded woods.

it is not a run on sentence but it does not flow well. may i suggest:

The truly astonishing aspect of it all is how Alec disregarded morality and took advantage of Tess’s exhaustion that she experienced in the woods.

No…but it’s not a very good sentence either.

The truely astonishing aspect of it all is how Alec disregared all morality and took full advantage of Tess’s state of exhaustion that one night in the shielded woods.

Actually not sure of the posessive of “Tess”.

Hm. A run-on sentence contains two complete thoughts – two parts that each have a subject and predicate – and the two parts are NOT dependent on each other to make sense (joined by “because,” “so,” etc.) Even though you join your two complete thoughts with “and,” your two complete thoughts really don’t follow each other; they are two different thoughts. It would be better to write, “When a man loves a woman, he asks for her hand in marriage. Once they fall out of love, they get a divorce.” Better for ACCURACY might be: “When a man loves a woman, he may ask for her hand in marriage. If they fall out of love, they may decide to get a divorce.”

A bit lenghty but i belive it is correct. It is not a run on sentence.

Its not, but maybe you should change it a bit. Possibly add some commas, periods, or some more conjunctions

yeahh, to me it is. you should try adding commas or just rewrite the sentence.

yea sonn