The first dog is bigger than the second one. The second dog is the biggest of them.
Open the links and do the exercises about comparison structures, copy your score in the commentary section and write 5 sentences more with this grammar structure using the images above. Have a nice afternoon!. NOTE. They are 3 exercises. O.K
http://web2.uvcs.uvic.ca/elc/studyzone/330/grammar/regcom2.htm
https://eflnet.com/grammar/compsupadj1.php