Paramathma also known as Parabrahman or highest atman is the ultimate destination where all atmans unite after moksha. Paramathma is the eternal truth, bliss, and knowledge. In Hinduism, Lord Shiva (The destroyer) and Lord Maha Vishnu (The preserver and the sustainer of the universe) are the two forms of Paramathma.
Paramathma is the first and foremost atman. He believed to have the highest level of knowledge and energy creates, preserves, sustains, and destroys all life. The Power and Energy of Paramathma is thought to be ineffable.
Paramathma is believed to have supermystical powers because of his penance. The Paramathma is the one who is in everything and an ananta(eternal or Infinite). The Atman is immortal as the Paramathma since all atmans are a part of Paramathma. He is a pure personification of everything beyond conceptualization and manifestation.