Which word suggests overwhelming by numbers or size?

The word "inundate" is the best choice to describe overwhelming by numbers or size because it specifically connotes being overwhelmed with a large quantity or volume of something, often associated with water or a flood of something that surpasses the capacity to handle it. Inundation implies an excessive influx that cannot be coped with easily, reflecting the aspect of abundance in size or numbers.

In contrast, while "flood" might suggest an overwhelming amount in a general sense, it mainly refers to the overflow of water and is not used as commonly in broader contexts. "Overwhelm" is a general term that indicates being overcome in a broader context but does not explicitly convey the idea of being swamped or flooded with large quantities. "Conquer" focuses more on defeating or gaining control over something rather than the concept of being overwhelmed numerically or in physical size.