All builds need direct damage (since you need to kill your enemies to win) but some also excel at crowd control.
You can try chemical pistol and watch your enemies slowly melt in acid while being immobilized as well as freeze or burn them.
Example basic build:
https://underrail.info/build/?HgUQBgMGAwdGNwDCoB4AAAAAAAAyAFAAAAAAAAAAAAA5ASZhwpFWWQ0RwqNOOjHCs-KyuwXita4K378Feats more or less in order.
You start the game with a normal pistol and once you reach Jukyard, you buy parts from Fixer to craft yourself an acid chem pistol. In the offhand you can either take cryopistol or fire pistol since mutants are immune to acid. Fire pistol can also help with triggering Ambush feat if you take it, while cryo pistol allows to trigger Execute in case you ae unable to stun them with the dirty kick