Frieren is around city block level or multi-city block level for destroying a cliff that a demon lifted with magic.Frieren verse gonna be the anime HP where it gets wanked beyond its level despite it's magic not really being that impressive?
The fact Frieren and Fern are good characters only makes it worse.
She also stated with her magic she could destroy a whole forest and even a village, so possibly town level.
Can track lightning magic and fight those who have reacted to it. Though since it’s only magical lightning (the series never elaborates if the elements replicate real elements like Black Clover or Fate) maybe around supersonic or hypersonic.
Here is also Frieren blocking Fern’s Zoltraak via mana blast after seeing it.
Here is Frieren sidestepping Solitaer’s mana blast