Salaaam....
What is the maximum someone can give as a will from his wealth to be distributed after his death?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

The maximum that someone can give as a will from his wealth in the Sharee'ah is one-third and it should be for a non-heir. Whatever exceeds one-third is not effective except with the consent of the heirs. Their consent should be that which is Islamically accepted, meaning the consent of those who are adult and rational.

The evidence about the impermissibility of exceeding one-third in the will is the Hadeeth of Sa’d ibn Abi Waqqaas who narrated: "The Prophet visited me during my illness. I said: I have property; May I bequeath all my property in Allah's Cause?" He said, "No." I said, "Half of it?" He said, "No." I said, "One-third of it?" He said, "One-third (is alright), yet it is still too much, for you'd better leave your inheritors wealthy than leaving them poor, begging of others." [Al-Bukhaari and Muslim]

Abu Hurayrah narrated that the Prophet said: "Allah has been charitable with you over the disposal of one third of your wealth at the time of your death, so that you may be able to add to the record of your good deeds." [Ahmad, Ibn Maajah and ad-Daaraqutni]

Ibn Qudaamah said:

"The will for a non-heir is obligatory in one third without the need for the approval of the heirs, but whatever exceeds one-third depends on their [heirs’] approval, so if they approve it, it is permissible, and if they reject it, it is void, according to the view of all the scholars." [End of quote]

Allah knows best.