Guati is a slur used to describe Guatemalans in a derogatory way. Same level of offensiveness as nigger or chink.
The word Guati is a racial slur that has been used historically to degrade and dehumanize guatemalans. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to guatemalans. If you are unsure about whether or not it is appropriate to use the word Guati, it is best to err on the side of caution and avoid using it in any situation.