There are many people in the world who are known for their amazing memory. However, to talk about the strongest memory, it is necessary to clarify the type of "memory" that is referred to.
If it refers to long-term memory, then no one can be called "strongest" for sure. This is because long-term memory is basically impossible to measure and compare accurately, and it is affected by many factors such as individual genetics, experience, learning strategies, etc.
However, if you mean short-term memory or working memory, there are already a few people who excel in this area and have a good reputation in the field. Here are some examples:
Oscar W. H. "Oz" Weinstein
Ozka Weinstein is a professor in the Department of Neurology at Harvard Medical School and a member of the American Memory Society. He specializes in studying the mechanisms and neurobiological basis of human short-term memory, and has demonstrated outstanding short-term memory levels in a variety of experiments.
Mattias Ribbing
Matt Cheekson is a Swedish orator, writer and memory guru who has won several international memory competitions. He is adept at using a variety of visual and associative techniques to memorize numbers, cards, letters, and other information, and is able to recall and reconstruct this information with astonishing speed and accuracy.
Andrew Budson
Andrew Boban is a professor in the Department of Neurology at Harvard Medical School and a member of the American Memory Society. He focuses on studying working memory performance in older adults and patients with Alzheimer's disease, and proposes some proven memory training methods and strategies.
Although no one can be called the "strongest" memory genius for sure, we can see from the above examples that there are already many outstanding experts and practitioners in short-term memory and working memory, whose research and experience are of positive significance for us to understand the mechanism of memory and improve our own memory ability.