The phrase "be at the bottom of" typically means to be the cause or source of something negative, but what about its antonyms? Perhaps the opposite of being at the bottom of something would be to be at the top or forefront of it. Another antonym could be to be on the surface or superficial level of something rather than deeply rooted within it. Additionally, instead of being the cause of something negative, one could be the catalyst for something positive. Ultimately, there are a variety of ways to express the opposite of being at the bottom of something, depending on the specific context and nuances of the situation.