Bhaktavatsala is none other than Lord Shiva himself, so called because he is very kind towards his devotees. He is also called Bholenath for this reason. Whoever offers prayers with at most dedication, Lord Shiva showers his grace upon them, irrespective of their race, cast, sect and gender. It is also very much evident in all the epics.
There are few devotees of Lord Shiva who have been categorized in the top level. Some of them demon king Ravana, Lord Brahma, child devotee Markandeya and the two associated of Lord Shiva Nandishwara and Nagendra. The demon King Ravana has been the most revered devotee to Lord Shiva. It is true that there is no other disciple to Shiva like Ravana.
Ravana starts praying Shiva even before entire world wakes up. He knows every Puja performed for praying Lord Shiva. Even at the time of war with Lord Rama, Ravana did perform the most critical pujas , not to win over Rama as he did not have fear of death, but to stay alive to offer prayers to Shiva. Such is his devotion towards Shiva.
Lord Brahma and Goddess Saraswati are said to be the foremost disciples of Lord Shiva. They knew that without the grace and permission of Lord Shiva, neither can Brahma create the beings, nor can Saraswati be the Goddess of Wisdom.
If Markendeya would not been a devotee to Lord Shiva, he could neither have taken birth, nor sustain the life after getting birth. In the same way, neither of Nandishwara and Nagendra could have gained such importance in the history, if they were not associated with Shiva.
Its wonderful about greatness of supreme Shiva. Sir, but you forgot to include lord Narayana in the above topic. Among the gods there is no other great shiva bhaktha higher than Lord Narayana. Lord Narayan plucked his eyes and offered to god shiva’s feet and achieved Sudarshana Chakra, attained sarva vyapakatva in universe as a kapila maharishi, parashurama attained parashu from god shiva, lord rama achieved pashupataastra from vishwanatha, And the great thing is lord narayana revealed 108 names of shiva and attained half body of Bhava. He has also given shiva sahasranama stotram (lingapuranantargath) to this world. Lord Krishna worshipped somnath Mahadev jyotirling. Gautham Buddha worshipped pashupatinath mahadev. Lord Narasimha Swamy has given 108 names of Lord Sharabeshwar(Shiva’s incarnation) after his pacification. The Supreme Shiva also given boon to lord narayan that lord vishnu (and his avtars)will be worshipped higher than himself and any other god in Kali Yuga. Lord Narayan always worships ‘Indraneela Lingam’. Before the universe evolved, lord narayana was the first deity to get blessed by God Shiva compared to lord brahma. Lord Narayana and Lord Brahma penance for Supreme Almighty for million divya varshas (1 divya varsha = lakh of years) then god shiva gave his darshan to them and upon their request and the pleased shiva has given method of worshipping him. Every avatar of lord narayan worshipped Shiva and he worships him forever (as revealed in Shiva mahapuran and lingapuran) . Lord Haygriva, Lord Dattatreya worshipped the first universal guru god Dakshinamurti and attained gurutva (guruship).
That is great significance of Lord Narayan’s Bhakti towards Great Vishwanath.
And the goddess Lakshmi is also a great devotee to parameshwar, he has given wealth to goddess mahalakshmi as result to her penance to Aishwaryeshwar Mahadev, and she also did worshipped to reunite with lord narayan.
The Supreme Shiva is god to all, no matter worshipper is Deva, Daanava, maanava, janthu etc. he bestows his incomparable blessings to his devotees and wants true bhakti nothing other than that.
jalandher was killed by bhole nath in puran