I'm looking for a single word describing a person who lends money to dynasties or kingdoms in large amounts? who does not lend small amounts to anyone, hence they generally do not lend to individuals.
In most cases such people lend money for interest and against some guarantee like house, land, gold or something on those lines.
Most probably a word should be old and may or may not be in use today.
do we have any single word describing such a person?
Try "financier".
The Cambridge Dictionary defines it as
a person who has control of a large amount of money and can give or lend it to people or organizations
A backer is someone, or an institution, providing (usually) financial support for an undertaking. Lexico has
backer
NOUN1 A person, institution, or country that supports someone or something, especially financially.
Which major backer would financially support a party that had no chance whatsoever of gaining political power?
Sometimes the payback isn't the usual monetary percentage, but a broader interest. For example a major engineering project such as a harbour or a railway might be supported, for the longer term goal of promoting lucrative trade.
There is no single word that describes what you want to describe. It would hardly ever see use. In fact, it's hard to think of a specific example in the real world. Even the largest banks are often willing to lend to individuals. Central Banks, such as the Federal Reserve, meet many of your criteria and they will generally not deal with individuals or with small transactions, so they come close, but they often do not require collateral and their lending function is often secondary to their other functions to the point they are sometimes called "lenders of last resort".
Your initial word of "lender" comes closest. It is broader than what you are looking for, but if used without any attachments, people will default to assuming it is a money lender. You can then explain that this specific lender meets your other criteria of not dealing with individuals, being large, etc. While not limited to them, this term is routinely applied to certain types of hedge funds, the federal reserve, and other entities that do meet most of your criteria in financial and legal documents so it is probably the best word you will find.
With credit to auspicious99 for pointing it out first, "financier" also comes close. However, it would include many others that do not. Merriam-Webster defines financier as:
1: one who specializes in raising and expending public money
2: one who deals with finance and investment on a large scale
A venture capitalist is likely a specific type of financier, especially if they help recruit other early stage investors. But a venture capitalist, at least while acting as such, is more likely to purchase equity than lend money. Also, while it is certainly proper to call a lender a financier, the term is more often applied to middlemen. It would fit the institution you want to describe, but it would also fit a lot of other things.
A usurer is someone who lends money at unreasonably-high levels of interest.
(There are some who consider all commercial interest rates to be ‘unreasonably high’, but that's not the usual meaning.)
"Patron" fits the bill.
A "patron" is someone who supports organizations, kingdoms or dynasties by lending money.
According to Cambridge English dictionary, patron is a person or group that supports an activity or organization, especially by giving money.
How about “Creditor”? This could be the word you are looking for.
What about 'loaner' ? It's a bit generic but it might work.
