I'm not confident that right now I could waltz into Riddle Manor (which I checked, there are heavy wards there now) and take on every heavy hitting inner circle member, plus the dark lord and not die. I mean, I could easily kill them all, that kinda comes with the territory of  having basically Ancient Elementals plus the power of Hell behind me and at my beck and call. The problem isn't power it's stamina. I have the power to content with Voldemort one on one for a short while but after that I need to draw from my contracts and the longer I do that the worse the price will be. and the same goes for all the death eaters. None of them bar Voldemort can stand up to the raw power I can wield but going after all of them would drain me to the point where killing the Dark Lord would literally be suicide. So I either need them to split up or I need to work on my Stamina. Just as a quick explanation since I just can't help myself, A person can't run out of magic, It's the fact that spells rely heavily on willpower, bending the world to your will takes a certain amount of mental effort, too much and you get mentally exhausted and your spells start to wane in power because you don't have the willpower to make them work. If you're particularly headstrong you could probably rise a castle straight out of the ground in first year if they wanted but they would pass out immediately after from the strain of it and probably be comatose if not severely brain damaged from the magical backlash. if you don't have the willpower for a spell and you try to force it, it will work but it takes a toll physically instead. That's why I can draw power from my contracts, they can hold back the physical repercussions until after I'm done but it comes at the previous mentioned and experienced price. This system does come with the benefit that the longer you use magic the easier spells become because it's like a mental version of muscle memory. Which is why the older a wizards is more powerful they are, they've been using magic so long it's like second nature to perform this amazing feats.