Probably it is Ibeabuchi who has had 26 years and 5 months between the fights. Anyway, name your other interesting examples of 10+ year layoffs.
Murad Khalidov had 11 and a half years out of Boxing, whilst being in prison for a long stretch and competing in other combat sports. But returned to boxing after 11 years aged 37 and impressively became the first to KO the usually granite chinned Sergey Kuzmin.
Professor Mike Donovan was gone from the pro scene for 12 years when he fought nonpareil Dempsey in 1888