A Saint who gives scripture based worship of the Supreme God to his followers is in essence a Complete Saint. He is the complete knower of all the four Vedas, six shastras, eighteen Purans etc i.e. he will explain their essence.
He imparts the True Mantra (Satnaam / सतनाम) to his followers which can lead to salvation. Read Identification of a True Saint
A Saint or Guru or preacher who does not have the information about the Supreme God is an incomplete Saint.
Therefore that incomplete saint is unable to impart the true path of worship to his / her followers as a result of which the followers are not able to attain salvation / Moksh / Nirvana.
All those saints who consider Shri Krishna or Shri Vishnu ji or Shiv ji or Brahma ji as the Supreme God are incomplete saints.
They are not familiar with the Bhagavad Gita or Vedas or Puraans (Vishnu Puran, Durga Puran, Shiv Puran etc.) because in all these Holy Scriptures these Gods themselves accept some other God to be the Supreme God. Read Who is the Supreme God?
All those saints who consider Shri Krishna or Shri Vishnu ji or Shiv ji or Brahma ji as eternal are incomplete saints.
Bhagavad Gita, Shiv Puran, Durga Puran and Vishu Puran clarify that Brahma, Vishnu and Shiva are in birth and death. Those who say that Braham, Vishnu and Shiv live for ever and never die are incomplete saints and have no knowledge about our Holy Scripture.
All those saints who say that God is formless are incomplete saints.
Our Holy scripture i.e. Shrimad Bhagavad Gita, Vedas, Shri Guru Granth Sahib, Bible, Quran Sharif etc clearly prove that God is in form. A saint who preaches that God is formless is an incomplete saint. Read Form of God
All those saints who profess arbitrary worship like doing Pilgrimages, carrying out Shraadhs, having a dip in River Ganga as a means of salvation, doing forced meditation etc are incomplete saints.
Holy scriptures do not profess pilgrimages, carrying out shraadhs, bathing in River Ganga or doing forced meditation. These are arbitrary way of worship and no salvation can be achieved by doing all these activities. A saint who asks his followers to do such things is an incomplete saint.
All those saints who impart arbitrary mantras like Om Namah Shivaay, Om Namo Bhagvate Vasudevaay, Om Tat Sat, Hare Krishan, Ram Ram, Hari Om Tat Sat etc are incomplete saints.
All the above mantras are arbitrary and have no mention in our Holy Scriptures apart from Om Tat Sat which is a coded mantra. A saint who imparts such naams to the disciples is an incomplete saint and is playing with the lives of his disciples by misleading them.