You can try:
sed '/<applicationForm>/,/<\/applicationForm>/d' file.log
if you are satisfied of the result (sent to standard output) then you can run the command again adding the -i
option to actually change the file content. Or use -i.bck
to keep a backup copy of the file itself, so that you can easily do a diff between the input and the output file. I would run multiple sed command to remove the different key pairs. Hope this helps.