I bought diablo 2 in a sale a few days ago and created an online character. Outside of peak hours this is a pretty good experience, but in the evening, everything feels incredibly laggy and unresponsive. 2 nights ago, it wouldn’t even let me log in, even though other online games worked just fine.
Because of this, I would like to turn my online character into an offline character. Is this possible?
No, you can’t transfer online to offline.
Alright. Couldn’t play 3 nights in a row, so I just created a new offline character from scratch 
I believe it’s much better to play online because your character/items are saved on blizzard cloud. Even if you reset or change your console your character it’s in a safe place and you can continue your game progress whatever you want as long as you login with your battle net account! With offline character you only get a local save…If you reset your console or something bad happen with your console, you will lose your char! Ready to risk?
I think all consoles offer a way to backup your saves to online storage, or to a usb device. Having possession of your own saves is better than trusting blizzard with. If your console dies, you can simply redownload them. But if your online characters purge, or your accounts get banned, they are just gone forever.