awk で実行できる場合は、次のワンライナーを確認してください。
awk -F'[}{]' '{split($2,a,",");delete(b);for(x in a)b[a[x]]}length(b)<=2' file
小さなテストをしましょう:
kent$ cat file
ok,{(XXX1),(XXX2)},whatever,unique=2
ok,{(XXX1),(XXX1),(XXX1),(XXX2)},whatever,unique=2
ok,{(XXX1)},whatever,unique=1
ok,{},whatever,unique=0
nok,{(XXX1),(XXX2),(XXX3),(XXX4)},whatever
kent$ awk -F'[}{]' '{split($2,a,",");delete(b);for(x in a)b[a[x]]}length(b)<=2' file
ok,{(XXX1),(XXX2)},whatever,unique=2
ok,{(XXX1),(XXX1),(XXX1),(XXX2)},whatever,unique=2
ok,{(XXX1)},whatever,unique=1
ok,{},whatever,unique=0
ご覧のとおり、nok
行が削除されました
編集
awk -F'[}{]' '{gsub(/[()]/,"");split($2,a,",");delete(b);for(x in a)b[a[x]];l=length(b)}l<=2&&l>0{s="";for(x in b)s=s""x",";sub(/,$/,"",s);y[s]=s $3}END{for(x in y)print y[x]}' file
テスト
kent$ cat file
{(XXX1),(XXX2)},whatever,unique=2
{(XXX1),(XXX1),(XXX1),(XXX2)},whatever,unique=2
{(XXX1)},whatever,unique=1
{},whatever,unique=0
{(XXX1),(XXX2),(XXX3),(XXX4)},whatever
kent$ awk -F'[}{]' '{gsub(/[()]/,"");split($2,a,",");delete(b);for(x in a)b[a[x]];l=length(b)}l<=2&&l>0{s="";for(x in b)s=s""x",";sub(/,$/,"",s);y[s]=s $3}END{for(x in y)print y[x]}' file
XXX1,XXX2,whatever,unique=2
XXX1,whatever,unique=1