"Rearmost" refers to the very last or furthest position in a group or sequence. It is used to describe something that is located at the back or end of a line. Full definition
Things aren't bad in the two rearmost seats of seven - seat versions, either. (whatcar.com)
Remarkably for any vehicle with three rows of seats, the Navigator's rearmost row is actually fairly comfortable for adults. (digitaltrends.com)
Whilst CONTINUALLY checking the chain tension, slowly turn the smaller rearmost swingarm adjustment nuts clockwise on both sides.. (mechanics.stackexchange.com)