Will a glass of wine be 'spoiled' if left out overnight? Or still ok to drink?!

It won't kill you, wine is actually mildly antimicrobial. That being said a sweet wine is food for a whole lot of microbes, most commonly wild yeast. Leave it out another few days and you'll see the colonies forming on the surface. But there is usually enough sulfur in the wine to inhibit growth for a couple of days. It will be oxidized, one quick way to tell is if the wine has turned slightly copper or brown.

Don't listen to what these people are saying about judging your wine drinking. As a winemaker I'm happy to see you drinking any sort of wine! I doubt you would notice one night of oxidation without comparison, but you can take this opportunity to learn something about wine. Try to recreate a fresh mix and compare it with the wine that was left out. See if you can see the difference in color and taste the oxidized character.

The wine should still be OK to drink, if left out overnight as long as the room temperature did not get too high (over 70F). Putting it in a container won't help it last any longer. I would drink as soon as possible and not leave out another night.
I would also chill a very little (15 min. in fridge) before drinking.
This has happened to me more than once and have had no problems any time.

If you put some cling film over it, or leave it in the fridge, it'll last for the night. In fact, it'll probably be ready for drinking in the afternoon the next day. I'm not a drinker, but my dad is, and that's where I found this out from.

Ma pa.

It won't hurt you to drink it but it won't have as good a taste. Why the heck would you mix those?

You could probably drink it but it obviously have lost much of its flavor itll be nasty...just dump it down the drain

Depends how desperate for a drink you are! Yes it will be spoiled.

The cling film & fridge will help keep it (I do this)

Otherwise taste it and find out!

most wines will oxidize. but a merlot /blush.(bleck)..that will be just fine

yes, no