What is the ruling on a partner withdrawing and demanding his entire capital back, while refusing to bear any losses, in addition to demanding a percentage of the compensations you are seeking, exploiting the absence of a written contract and his knowledge of the business's failure?

The loss is borne by all partners according to each one's capital. Thus, the reduction is proportionate to the two capitals, as stated in the Mudawwanah, Nasb al-Rayah, Kashshaf al-Qina', and al-Mughni. This is a matter of consensus among scholars. A partner is not allowed to refuse to share the loss with the other partners, unless it is proven that one of the partners committed an act of transgression or negligence, in which case the transgressor or negligent party alone bears the loss. Since this matter involves a dispute, an inquiry from afar is insufficient; rather, it should be presented to the Sharia courts or scholarly authorities should be consulted in person so that the mufti can hear from both parties of the claim.