"More whacking" refers to an increase in forceful and vigorous action. There are plenty of synonyms that convey a similar sense of intensity. One option is "heavier-handed," which describes someone who uses more force than necessary. Another option is "hard-hitting," which suggests a powerful and effective blow. "Hammering" is another choice and connotes a repetitive, forceful action. "Pummeling" or "thrashing" also work as synonyms, with the former suggesting a series of repeated blows and the latter indicating a more intense and sustained attack. In any case, all of these words imply a heightened level of force or impact, similar to the phrase "more whacking".