Sorry, this isn't a chapter. I was recently asked this question and I have noticed a lot of people seem to be confused about power level. Power is the body's potential to cast and manipulate raw magic. Higher power means more magic output. Power is not a measure of skill, experience, or strategy. So, higher power doesn't necessarily mean the stronger person would win. Here's a list of important characters and their power level. Power levels are from 1 to 100, 100 being the highest:
Avg First Year Student: 05
Avg Second Year Student: 08
Avg Third Year Student: 11
Avg Fourth Year Student: 15
Avg Fifth Year Student: 19
Avg Sixth Year Student: 25
Avg Seventh Year Student: 30
Avg Adult: 35
Avg Auror: 42
Avg DE: 37
Avg Inner Circle DE: 47 *Inner circle are the elite DE commanders of Voldemort
Current Power Levels of some Important characters:
Hermione Granger: 12 *Hermione is smart, not strong
Ronald Weasley: 17
Draco Malfoy: 17
Daphne Greengrass: 20
Viktor Krum: 37
Fleur Delacour: 30
Damian Greengrass: 50
Bellatrix Lestrange 57
James Potter: 57
Lily Potter: 41
Sirius Black: 50
Peter Pettigrew: 32
Remus Lupin: 39
Voldemort: 90 *Result of already significant magical core expanded through rituals and sacrifice
Dumbledore: 75 *Dumbledore is weaker than Voldemort in terms of raw power but makes up the difference with his knowledge, experience and control/efficiency
Neville Longbottom: 50 *BWL, his already larger magic core is further expanded as his innate magic has had to constantly battle the horcrux and keep it at bay which increased his core abnormally
Harry Potter: 25 *This is the level at which Neville would be if there was no horcrux. Harry is much stronger than his peers, with power levels matching sixth year students already. But can't be compared to BWL
Neville(eventual expected Power Level): 90
Harry(eventual expected Power Level): 60 *can be more with rituals and sacrifice
Hope this clarifies a lot of doubts. I will add more as I think of them.