DH has always struggled to get the DC to listen to him. This is mainly because he'll repeatedly ask but there'll be no consequences (though he threatens there will be) if they don't listen. I back him up, but it's not really working as obviously if I'm not there then hes stuck. His recent approach has been to ignore them if they won't listen to him but in.some circumstances this has meant leaving them in dangerous situations.
For example:
He had the toddler sitting on the side in the kitchen while he made a drink. He told her they were going in the other room now. She refused and said she wants to stay there, so he left her there. Next to hob (though not on) and with a drop onto concrete tiles.
He wanted to put a bag in the car after school which was on the opposite side of a 40mph road. DD (6) said she didn't want to, so he left her on the other side calling for her bag. Now I'm fairly certain she wouldn't try and cross, but I wouldn't have taken that risk.
We have a car park about 30 metres from our house. If the DC are taking a while to get out (I.e. Looking for something they've dropped) he'll just leave them and go indoors, ignoring the fact that's leaving them to cross a car park by themselves.
If we are out and DD is on her bike then one of us needs to be close as she's still a bit unstable. I was following her the other day and toddler refused to leave where we were (feeding ducks off a bridge near a road.). Rather than stay to retrieve toddler, DH left her because she wouldn't listen!
Now it's all come to a head because we are camping in Wales at the moment. Yesterday we were climbing and playing on rocks/in a fair sized waterfall. Toddler and I went to change hernappy, lleaving DH and DD splashing. I get distracted as toddler needs a drink and snack. Go back 10-15 mins later and find DD climbing rocks on the other side of the waterfall alone, while DH is sitting on this side (a good 30m from her and unable to hear one another over water) playing on his phone. When I asked why he's left her alone he shrugged and said she wouldn't listen when he wanted to be finished 
These are just a few examples but the last one has really angered me. She could've fallen, banged her head and been under water and he wouldn't have known. AIBU to think he is being completely ineffectual and that you can't just leave DC in these instances?