x1 is superlative in property x2 (ka), the x3 extreme (ka; default ka zmadu) among set/range x4.
Also: x1 is x3-est/utmost in x2 among x4; x1 is the x3 end of x4; x1 is extreme; x1 is simply x3. (cf. cmavo list rai, jimte, milxe, mutce, note contrast with milxe and mutce rather than with mleca and zmadu, which are values for x3, banli, curve, fanmo, krasi, manfo, prane)