but it [Electrum] is not the safest because you have to trust someone else to give you the right data.
FYI Electrum implements SPV—Electrum servers cannot "invent" non-existent transactions.
Electrum servers
could withhold one more transactions, however because there are multiple servers operated by (allegedly) independent parties, multiple parties would have to collude to pull this off (or someone would have to control your Internet connection).