A piece of code that will allow you to spam with reactions on a new message in a chat. Requires telethon installed.

telegram_reactor.py

from telethon import TelegramClient, events, types
from telethon.tl.functions.messages import SendReactionRequest
from telethon.errors.rpcerrorlist import ReactionInvalidError

import random

# Config from https://my.telegram.org/auth

api_id = 123456 # your api id here
api_hash = 'aajwjwjwjwjwiwiwisdjsdjsddsk' # you api hash here 
chat_to_react = 'My chat' # Chat name or ID if possible

# Create a Telegram client with your API ID and API hash

client = TelegramClient('session_name', api_id, api_hash)

# Define a list of possible reactions

reactions = ['❤️', '👍', '😢', '🥰', '😡', '🤯', '🤣', '😍', '🤡', '🙉', '😱', '🤩', '😨', '🍌', '🖕', '🤮', '💊', '🏆', '😇', '👌', '😭', '👎', '🔥', '👏', '🤔', '🤬', '🎉', '💩', '🙏', '🕊', '🥱', '🥴', '🐳', '🌚', '🌭', '💯', '⚡️', '💔', '🤨', '😐', '🍓', '🍾', '💋', '😈', '😴', '🤓', '👻', '👀', '🎃', '🙈', '🤝', '✍️', '🤗', '🫡', '🎅', '💅', '🤪', '🗿', '🆒', '💘', '🦄', '😘', '🙊', '😎', '👾', '🤷', '☃️', '🎄', '😁',

            '\u2764\uFE0F\u200D\U0001f525', # heart on fire 
            '\U0001F937\u200D♂️', # blue man doesn't know
            '\U0001F468\u200D\U0001F4BB', # man on the laptop 
            '\U0001F937\u200D♀️' # woman doesn't know

        ]

# Handler

@client.on(events.NewMessage(chats=[chat_to_react]))
async def react(event):
    async def _react():
        reaction = random.choice(reactions)

        try:
            await client(SendReactionRequest(
                peer=await event.get_chat(),
                msg_id=event.id,
                reaction=[types.ReactionEmoji(
                    emoticon=reaction
                )]
            ))
        except ReactionInvalidError:
            print(f'This reaction {reaction} is not possible')
            await _react()

    await _react()

client.start()
client.run_until_disconnected()