some that come to my mind are:
% of synergy target realized, % synergies vs total cost base
% employee attrition, perhaps as variance vs previous periods
% change in absenteeism
% revenue lost (e.g. loss of customers)
% change in key process KPIs (where these KPIs depend on the industry), i.e. did the business get better / more efficient
integration spend vs budget
% share value change
survey scores, e.g. internal employee surveys
