As you should already know to improve revenue profits is a positive effect on diversity. Another positive effect is reduced competition ( market more attractive). Greater capabilities (e.g. technology, capacity, innovation). Also better market access ( e.g. distribution, new territories.
However the negative effects I'm more driven, One-off costs and effect of integration (disruptive for both buyer and target business). too much focus on cost synergies can damaged be revenue & growth potential. Along with cultural conflicts. as well as risk of overpayment for the transaction.