As a perpetual low ball offer type of person you have to realize something. In todays market you are not going to get a lowball offer accepted with an MLS deal unless you are the only offer, or can close quickly and in all cash etc. So I would recommend going outside of the MLS - if you have no competition on offers you are more likely to get offers accepted.
The other thing is this. If you support the offer with evidence you'll have better luck. I have made offers with agents and said it is a standing offer, or been told no and a few days later have the seller come back with a lower number. If you know you numbers and are forceful in doing so you won't have any issues.
This is basically a go between on a the last property I purchased:
Agent: Nobody is buying this house wholesale
Me: Would it be okay if I reach out in a month to see if the seller has changed there mind when it is still for sale?
A few days later...
Agent: Would you be able to close quickly if I could get you in at 25k?
Me: No it would have to be 24k...
A few minutes later... offer accepted.
This specific instance I was being a pain in the *** just to be a pain in the ***. I almost never accept the first counter offer someone makes me. To me it seems that there is more meat on the bone.
I legitimately enjoy negotiating and honestly if someone thinks I am an ******* they probably are not wrong... Do I care if I potentially piss off a stranger with a low ball offer? Not really. That being said I also do immediately identify myself as a bottom of the barrel guy when someone asks me do you have an interest in XXX property.