User blog comment:B214/Question and Answers 6/@comment-185.112.105.215-20161221212616/@comment-10330822-20161222013411

Hand-to-hand combatant basically means you are skilled in hand-to-hand, or fist fighting. Immense combat skills implies that your mastery of skills go beyond just fist fighting, like swordsmanship or, in Sun Wukong case, stuff like staffs.

An example would be someone like Vasco Strada, who has immense combat skills, and was capable of taking on master hand-to-hand combatants and master swordsmen at the same time with a combination of extreme levels of hand-to-hand and swordsmanship.

Basically, if someone like Ise mastered swordsmanship and incorporated it into his fighting style, and fought multiple users of hand-to-hand and swordsmanship at the same time, you might consider him to have "Immense Combat Skills".

Of course, other words are used for this, for Sun Wukong the wikia has him listed as a "Master Combatant", but it roughly means the same thing.