aaa<vvv>bbb<vvv>ccc
xxx<vvv>yyy<vvv>zzz
aaa<vvv>new<vvv>new2
111<vvv>222<vvv>333

aaa<vvv>bbb<vvv>ccc
xxx<vvv>yyy<vvv>zzz
111<vvv>222<vvv>333

$ awk -v OFS="<" '{ print NR, $0 }' file | sort -t '<' -u -k2,2 | sort -t '<' -k1,1n | cut -d '<' -f 2-
aaa<vvv>bbb<vvv>ccc
xxx<vvv>yyy<vvv>zzz
111<vvv>222<vvv>333

1<aaa<vvv>bbb<vvv>ccc
2<xxx<vvv>yyy<vvv>zzz
3<aaa<vvv>new<vvv>new2
4<111<vvv>222<vvv>333

4<111<vvv>222<vvv>333
1<aaa<vvv>bbb<vvv>ccc
2<xxx<vvv>yyy<vvv>zzz

1<aaa<vvv>bbb<vvv>ccc
2<xxx<vvv>yyy<vvv>zzz
4<111<vvv>222<vvv>333

$ sort -t '<' -u -k1,1 file
111<vvv>222<vvv>333
aaa<vvv>bbb<vvv>ccc
xxx<vvv>yyy<vvv>zzz

$ awk -F '<' '!seen[$1]++' file
aaa<vvv>bbb<vvv>ccc
xxx<vvv>yyy<vvv>zzz
111<vvv>222<vvv>333

$ sed '=' file | sed 'N;s/n/</' | sort -t"<" -u -k2,2 | sort -t"<" -k1,1 | sed 's/^[0-9]*<//'
aaa<vvv>bbb<vvv>ccc
xxx<vvv>yyy<vvv>zzz
111<vvv>222<vvv>333