If you illegally sublet an apartment can the landlord (is it likely?) do anything besides kick you out? Can they keep the security deposit?

The deposit generally remains the property of the tenant until the landlord can prove they somehow "earned" it by having unpaid claims against the former tenant. If you pay everything you owe, they have no claim and must return your deposit to avoid being sued. Some states allow you to claim double or triple whatever amount they unlawfully withheld, plus your attorneys' fees. State laws vary, and it may also be possible that your lease contains legally enforceable forfeiture language.

Yes they can keep your security deposit as a penalty for your violating the lease. And if you have a lease, they can sue for the balance of it.

They can evict you, and what he can collect varies by state, but yes, he may be able to keep deposit, read your lease.

you're violating the lease and they can sue you.

Yes. They can also sue you for more money.

Yes. He will keep your deposit and apply it to the legal fees thst he incurred for your eviction. He will then send you a bill for the costs to repair any damage you caused as well as the balance of the legal fees.

You can be sure that they are highly likely to... also sue you for breach of contract, evict and claim their legal costs too

State laws apply, but that is not typically something states allow a security deposit to be kept for. Security deposits are to help cover financial losses from the tenant such as physical damage, cleaning, or in some cases loss of rental income.

most likely the illegal "tenant" AND any others in the unit will be evicted

Yes they'll evict you for violating the lease and yes, they'll most likely keep the security deposit too.