To lessen something is to make it less, or to reduce it. If you hope to lessen the chances of something bad happening, you want to make the number of chances fewer. Mitigate is a strong synonym for lessen, but this verb is used especially to talk about making things more bearable or giving relief, as to someone in pain or sorrow. It’s also used to talk about making things less severe: to mitigate the effects of climate change. Mitigate is sometimes confused with the similar sounding verb militate, which means “to have effect or influence.” This mix-up often occurs in the use of the phrase mitigate against, e.g., This criticism in no way mitigates (read militates) against your going ahead with your research. Although this use of mitigate occasionally occurs in edited writing, it is rare and is widely regarded as an error.
Something that’s so-so is neither very good nor very bad. If you go to a concert and report back that it was so-so, it means that you neither loved nor loathed the show. Rather, it was okay. Mediocre is another way to describe things that are middling or average. Though keep in mind, that describing something as average is, generally speaking, not exactly a glowing review! While this adjective appears on paper to be neutral, in most applications, mediocre suggests at best mere adequacy, as in a car that gets mediocre mileage, or at worst inferiority or poor quality: Mediocre construction makes that building dangerous.
The noun chaos is defined as “a state of utter confusion and disorder.” It is applied to a broad range of situations that lack organization. For example, a virtual work meeting wherein everyone talks over each other and there is no agenda laid out might be described as chaos. Or, on a larger and more serious scale, a poorly managed response to a disaster wherein nobody knows how to get the help they need might be described as chaos. The synonym pandemonium suggests unrestrained disorder marked by panic, uproar, and tumult. This noun, from Pandæmonium, the capital of the underworld in Milton’s Paradise Lost, burns a little hotter, so to speak. Pandemonium implies not just disorder, but also noisy, wild, and possibly even violent activity.