>>51731235Ghost/Grass/Steel already covers most types. Your main issue is going to be Dark/Fire, Dark/Steel, Normal/Fire, and Normal/Steel, which are the only type combinations to resist your STAB. There are three main types you want to look for
>Fighting covers the type that resist Ghost, but only allows you to hit 58.2% of the dex for SE damage and Dhelmise's only good Fighting moves are Body Press and Brick Break, which are less than ideal>Ground also covers all those types and gives you access to Earthquake, but Ground immunities are common, and a Flying/Fire type will still only take neutral from Poltergeist while resisting everything else>Ice and Flying, while not being able to cover those type combinations, each cover the most Pokemon, hitting a whopping 61.3% of all Pokemon for SE damage, though Dhelmise doesn't learn any good moves of either type.Ultimately I'd say go for Ground or Fighting. Rock is a decent alternative that lets you snuff Flying types that could be predicting a Ground type switch in, but you'd be relying on the Tera Move for your damage.
